Scoping primary ignition signal on car - help please! - Page 1
Forum section: electronics / projects

author: ssashton
author_rank: Frequent Contributor
timestamp: November 11, 2020, 01:32:47 pm
content: Hi all,My car has been acting up and I would like to scope the ignition signal coming from the ECU to see if it looks reasonable.I could really do with some help because I have no idea what I'm really doingI have a PicoScope 2203 (20V max. range, plus a x10 probe).My car is a Mini Cooper S (2007) which has 'pencil' ignition coils. I have swapped these out and I'm sure they are not the issue. So rather than probe the HT secondary ignition side, it seems easier to probe the primary side from the ECU.Tips on how to best do this are appreciated!Looking at cylinder 1 should I probe across the green and orange wires?Is the 20v range with x10 probe going to be enough to cope with the signal, as I expect there will be some kickback from the coil?Will anyone be able to tell me if the signal waveform looks reasonable?I do get a spark, but I have bad misfiring while almost every mechanical test is perfect. I'm thinking if something like a capacitor went bad in the ECU I could still get a spark but with a totally wrong waveform.

author: Miyuki
author_rank: Frequent Contributor
timestamp: November 11, 2020, 02:23:36 pm
content: All data shall be available in modern ECU, diagnostics of each coil, current and waveform, shall detect even wear on spark plugAnd also voltage on coil can be over 200V, commonly is clamped to 400-600V at driver transistor

author: Mazo
author_rank: Regular Contributor
timestamp: November 11, 2020, 02:58:14 pm
content: Most probably "logic" coils,aka the driver transistor is integrated,and you will see only a logic signal.

author: jonpaul
author_rank: Super Contributor
timestamp: November 11, 2020, 02:59:55 pm
content: Primary transients due to stored energy will kill your USB scope and perhaps PC.Get a real ignition analyzer, perhaps $100 on epay.Keep scopes and electronics FAR from ANY ignition work on cars EVEN AT THE PRIMARY.Jon

author: ssashton
author_rank: Frequent Contributor
timestamp: November 11, 2020, 03:40:14 pm
content: Thanks for the feedback guys!Amazing I can get better car diag. info here than auto forumsI'm not sure if they are 'logic coils' or not, would it be possible to know from the part number? They areDelphi 12137575010I'm not sure if this counts as a modern car and ECU, it's from 2007. I certainly don't get all that info about the ignition on my reader device but I am booked at the garage who have the proper BMW diag. kit which can tell more I hope!Trouble I find is that most garage do not have anyone who knows much about electronics, so they would not be likely to scope waveforms, just read data from the test gear.

author: bdunham7
author_rank: Super Contributor
timestamp: November 11, 2020, 03:58:14 pm
content: You would need 100X probes to be reasonably safe, and with ignition systems you have a lot of energy so fault conditions can be unpredictable. If everything is connected, the system should be well clamped to under 1kV on the primary side, but most scopes that are intended for use on ignition coils have a lot of extra protection. If you do get a primary waveform, I can look at it for you.Have you removed and inspected the spark plugs? Is the misfiring random or rythmic when it occurs? At idle, under load,

author: Tom45
author_rank: Frequent Contributor
timestamp: November 11, 2020, 04:11:37 pm
content: I would start with the basics. Disconnect the wire from one plug at a time and see how it runs. If you disconnect from a good cylinder it will run a lot worse. If you disconnect from a bad cylinder it will not change by much. That should at least narrow down where to look.Next try replacing or swapping plugs. And do a compression test at least on the bad cylinder.Apologies if you have already done this.

author: ssashton
author_rank: Frequent Contributor
timestamp: November 11, 2020, 04:54:54 pm
content: I think I might have found the issue. I did a leak-down / pressure test just now and it seems to blow out from cylinder 2 in to cylinder 1. Although I could not repeat the result after checking other cylinders and rotating the engine a few times. Still it did happen and I'm pretty sure it's not suppose to! I think the engine compression is over 200psi so the problem would be exacerbated compared with my test.Strange thing is, I get sooty spark plugs on all cylinders, even though I only see this blow out between C1 and C2. Maybe the ECU is trying to compensate and everything gets messed up?https://youtu.be/4z29lCQMxjMCompression test was done early on and seemed just fine. Guess I'm now a fan of leak down tests!

author: Johnny10
author_rank: Frequent Contributor
timestamp: November 11, 2020, 05:07:06 pm
content: There is great information and graphs of all sorts of auto tests with scope on the PICOtech.com site and Picoauto.comAlso:

author: bdunham7
author_rank: Super Contributor
timestamp: November 11, 2020, 05:32:46 pm
content: Quote from: ssashton on November 11, 2020, 04:54:54 pmYou may have carboned up intake valves. Try to repeat the test with something removed from the intake plumbing so that any intake manifold pressure is vented. You can't just open the throttle because it is electrically controlled, but you can find some vacuum fitting, as big as possible, and take it off. There are methods for cleaning the intake valvesin situ, but I don't know how effective they would be at this point.

author: ssashton
author_rank: Frequent Contributor
timestamp: November 11, 2020, 06:55:27 pm
content: Intake manifold is vented via the tube you see top left. Also compression test was okay. I'll have another crack at it tomorrow see if I can reproduce the results. ECU reader tool shows misfires on C1 and C2 which matches.

author: Miyuki
author_rank: Frequent Contributor
timestamp: November 11, 2020, 07:42:40 pm
content: It can be even an injection or fuel issueI had once a similar problem and it was fuel pressure, needed new fuel pumpAnd Ford misfiring all the time because it has crap biodegradable insulation on wires and has a million random shorts and glitches

author: bdunham7
author_rank: Super Contributor
timestamp: November 11, 2020, 07:53:40 pm
content: Quote from: ssashton on November 11, 2020, 06:55:27 pmDoes any air come out that vent? If it does what you show, then either the air is going out one valve and in another--either exhaust or intake--or you have a blown head gasket, which should show up reliably not intermittently. The intakes are famous for carboning up and not closing properly and they can do that intermittently. The exhaust valves can fail, but generally not a in a way that is intermittent. Keep in mind on a compression test, if the valve closes 2 out of 3 times, you'll get a good test. You would have to do the test repeatedly and watch the gauge closely to actually see the valve-not-sealing event happen.

author: ssashton
author_rank: Frequent Contributor
timestamp: November 11, 2020, 10:44:47 pm
content: Ordered a proper dual gauge leak down tester. I'll get back to you on how it goes.

author: joeqsmith
author_rank: Super Contributor
timestamp: November 12, 2020, 01:42:21 am
content: For my own motors, I just check the cranking pressure for overall health. With the throttle closed and some overlap, sure, I would expect there to be some cross over.As it's been said, misfire could be caused by a lot of things, not just the ignition. Easy enough to swap the coils and see if it tracks.

author: ssashton
author_rank: Frequent Contributor
timestamp: November 12, 2020, 01:24:58 pm
content: Well my leak-down tester already showed up that was fast!The instructions say I should calibrate the leak gauge. At the moment it maxes out at just 15psi, beyond that it just pegs the gauge regardless of leaking or not.Am I just stupid, I can't see any adjustment screws, just two on the back that hold the gauge on the screw post. Nothing under the rubber cover and the case doesn't want to come apart easily. How do I calibrate it?

author: bdunham7
author_rank: Super Contributor
timestamp: November 12, 2020, 03:54:53 pm
content: You haven't shown the entire instrument including hose ends, but I presume there is a way to shut off the hose that goes to the cylinder? If so, you've already calibrated it--you shut off the hose, set the pressure so that the gauge reads 0% leakage (top of the 'SET' region) and then connect it to the cylinder and read the leakage. This is a simple relative test and the percentages don't mean much except that you can compare the cylinders. Actual 'calibrated' leak testers have specific orifices intended to give a repeatable result when used with specific engines, typically aircraft engines where a maximum leakage value is specified. Just do the stest the same way for each cylinder, and if one is low, determine where the air is leaking to.

author: drussell
author_rank: Super Contributor
timestamp: November 12, 2020, 04:59:15 pm
content: I use the magnetic-core inductive pickup clampy-thing from my ancient, cheap-ass Equus timing light (has a removable cord) connected to the scope on the spark-plug-wire side. Lets me stick it either on the coil wire to the distributor, or on an individual plug. (Haha, it looks like they still sell the same model ~30 years laterhttps://www.amazon.ca/Equus-Dual-Inductive-Timing-Light/dp/B07Z6MXJNS)Works more than well enough to "see" what's going on with ignition events.I expect that any loosely-coupled pickup wrapped around a plug wire would be fine. The same concept could probably be used to pick up a signal from the primary side without actually physically connecting your scope to the circuit in any way.

author: Johnny10
author_rank: Frequent Contributor
timestamp: November 12, 2020, 05:22:57 pm
content: If you have a scope and a pressure transducer.You can do the following.This was one of my first projects back in early days of my electronics hobby.You can actually see the closing and sealing of the valves.I did this test with a Rigol 1052 scope and a simple 200PSi Pressure Transducer attached to a cylinder compression connector.Found a faulty sintered valve seat causing my misfire at low idle.

author: ssashton
author_rank: Frequent Contributor
timestamp: November 12, 2020, 06:17:34 pm
content: Quote from: bdunham7 on November 12, 2020, 03:54:53 pmI get what you mean, but 15psi is not enough for a leak down test. It needs to be around 100psi.

author: ssashton
author_rank: Frequent Contributor
timestamp: November 12, 2020, 06:19:39 pm
content: Quote from: Johnny10 on November 12, 2020, 05:22:57 pmI was encouraged to post my question here because I dug up your old thread!I don't have a pressure transducer. Are there ones that come ready to attach on a hose?

author: ssashton
author_rank: Frequent Contributor
timestamp: November 12, 2020, 06:20:44 pm
content: Quote from: drussell on November 12, 2020, 04:59:15 pmUnfortunately that is not practically possible with 'pencil coils' as the HT output is buried in the head.

author: Johnny10
author_rank: Frequent Contributor
timestamp: November 12, 2020, 06:54:55 pm
content: CoolThe threaded connection on one end fits 1/4 NPT male air fitting which connects into Spark plug adapter.I think I paid about 25-35 for transducer off eBay and also purchased a compression tester kit.You take out the spring stop valve so the pressure transducer can breath the up and down pressure variation.

author: bdunham7
author_rank: Super Contributor
timestamp: November 12, 2020, 06:56:56 pm
content: Quote from: ssashton on November 12, 2020, 06:17:34 pmProfessional leak down testers typically use 75-100psi as the set pressure, yes. I've also seen them lower. 15 psi seems odd, but the way I've described setting it up is how it works. What do your gauges read if you disconnect everything?

author: tpowell1830
author_rank: Frequent Contributor
timestamp: November 12, 2020, 07:16:34 pm
content: Quote from: ssashton on November 11, 2020, 04:54:54 pmWell, I have one question: Did your engine overheat recently? The head gasket could have blown or you could have a warped head. This could explain the crossover leakage.Hope this helps...

author: drussell
author_rank: Super Contributor
timestamp: November 12, 2020, 09:32:14 pm
content: Quote from: ssashton on November 12, 2020, 06:20:44 pmI know, which is why I said:Quote from: drussell on November 12, 2020, 04:59:15 pm

author: mikerj
author_rank: Super Contributor
timestamp: November 13, 2020, 10:48:35 am
content: Quote from: bdunham7 on November 11, 2020, 05:32:46 pm"May" is much too weak a word, it's extremely likely as these Prince engines are notorious for sticking valves due to carbon build up and it explains the symptoms. They are pretty terrible engines all round tbh, with a long history of poor reliability including failing timing chains and high pressure fuel pump, though carbon build up is the most common problem.The video shows cylinder two on a compression stroke (correct for a leakdown test) which means cylinder 1 will be on the intake stroke. A sticking inlet valve on cylinder 2 means there is a direct air path to cylinder 1 via the intake manifold. The fact that it doesn't always do it is even stronger evidence of a sticking valve. Time to get the intake manifold off and survey the mess within the ports.Quote from: ssashton on November 12, 2020, 06:20:44 pmIt's both possible and practical; you just need to extend the output of the coil with a suitable HT lead.

author: Renate
author_rank: Super Contributor
timestamp: November 13, 2020, 12:45:07 pm
content: This thread got me interested enough to check my 1995 Chevy G30 454 V8.It's a single coil with the driver built into the distributor, but there is a handy wire out for the tach (low end of the coil).I just put my Hantek scope on it on 50V/div and got textbook waveforms off of it, peaking at about 250 V.Unfortunately, camshaft position sensors only came in the 1996.I guess that a regular shop analyzer uses an inductive clamp to identify cylinder #1?I was thinking of maybe throwing a little magnet on the far end of the rotor and a Hall effect on the outside of the cap.It would kind of be cool to add the analyzer option to my little OLED (and the associated Android app).(I replaced the blue OLED with a bigger yellow OLED, but I don't have a photo offhand.)

author: SilverSolder
author_rank: Super Contributor
timestamp: November 13, 2020, 03:45:16 pm
content: Quote from: Renate on November 13, 2020, 12:45:07 pmLove the OLED project!

author: ssashton
author_rank: Frequent Contributor
timestamp: November 13, 2020, 04:06:52 pm
content: I only started this thread to specifically ask about 'scoping the ignition. However it seems you guys have extensive knowledge about cars so I owe you the full details of the symptoms. It's a long story but I want to give you all the infoThe car had been running reliably but with a slight misfire at low idle or under high boost. In normal driving conditions it was lovely. Over the last few months it started to develop a bit of kangarooing, meaning it would jump about slightly. This would happen particularly when trying to maintain a slow but steady speed. Under normal acceleration it was actually smoother.All of a sudden while going along the street at a gentle 40mph it began to run super rough. Felt like multiple cylinders. Thankfully it got me home. Then the car refused to start.I inspected the spark outside the engine while cranking and could see it arcing. I swapped in a used ignition coil one cylinder at a time and noticed no changes.My ECU reader told me there was no high pressure fuel feed - only the tank feed pressure (but no error codes). This is a turbo charged direct injection engine so it has a high pressure pump as well as the tank one.I suspected the high pressure pump but before shelling out on that, I swapped in an array of used sensors and also checked the wiring for each - MAP, cam, crank and boost pressure sensors plus injection and ignition wiring. No changes and all wiring good under 500mA load.I replaced the high pressure fuel pump. It still didn't give me any more pressure but after endless cranking the pressure came back and it started up (far longer than the fuel needed just to feed through).It still ran super rough, almost stalling and the fuel pressure was fluctuating a lot.On a hunch I put my old high pressure fuel pump back on, it also worked again! So it wasn't actually the HPFP which made the difference.I proceeded to replace the low pressure fuel pump and pressure regulator (low pressure regulator, HPFP has integrated pressure regulator for the high side) as this might cause pressure fluctuations. I also sucked the fuel out the tank and put in fresh fuel, in case someone had decided to try a nasty trick on me.At the same time I put 4 used (but cleaned and tested) injectors in the car in case they were the culprit. Plus 4 new spark plugs.No change, all the same with massive missfire and all spark plugs dry sooty after just 1 min running.At this point I came here wondering about the ECU output to the ignition coils. However I have sent the ECU toECUtesting.comand they have sent it back with a clean bill of health and the following report:Quote from: ECUtesting.comI don't fully know how they tested all the aspects of the ECU but I suppose I need to trust their ability. If they found a fault they could have charged me to repair it!At this point I'm inclined to take the head off regardless of leak down test results. I'll be able to replace the head gasket, clean and lap/re-seat the valves and swap the valve stem seals. It would just really suck to do all that and still have a non-working motor!!I can't imagine anything else that could be wrong given all I've tried to date.Oh, I don't believe I have vacuum leaks. I did have one in the past and the ECU detected it with an error code showing up. Not the case here.I really appreciate all the help you have been giving me!

author: bdunham7
author_rank: Super Contributor
timestamp: November 13, 2020, 04:32:28 pm
content: So have you tried the leak-down test??

author: SilverSolder
author_rank: Super Contributor
timestamp: November 13, 2020, 04:34:45 pm
content: And all of this is happening with no codes being flagged in the ECU at all, not even a misfire detection?The OBDII spec (which definitely applies to your vehicle model year) requires that the ECU be able to detect cylinder misfires - it should tell you exactly which cylinder(s) are involved (by measuring the change in crank speed after each combustion event).You can learn an awful lot from this article:https://www.brakeandfrontend.com/tech-feature-detecting-misfires-in-obd-ii-engines/

author: fcb
author_rank: Super Contributor
timestamp: November 13, 2020, 05:12:20 pm
content: I've got an '03 Cooper (not the 'S') and it does something similar sometimes when cold.The other night I drove it through a big puddle and it started doing it whilst warm - my theory is that it's something to do with either the timing pick-up (and hence firing at the wrong time) or possibly a knock sensor. Another thought was a the Air Mass system, possibly leaning off the mixture. If it was subtle then it probably wouldn't be picked up by the OBDII.

author: ssashton
author_rank: Frequent Contributor
timestamp: November 13, 2020, 05:21:52 pm
content: Quote from: SilverSolder on November 13, 2020, 04:34:45 pmThanks I'll look over the link.There are no ECU codes stored, but my cheap reader does show missfires on C1 and C2. However I'm not sure I trust the data as the device seems rather buggy (Creator C310). Plus, I see sooty spark plugs on ALL cylinders.

author: Renate
author_rank: Super Contributor
timestamp: November 13, 2020, 05:50:56 pm
content: Sooty spark plugs?Can you see your O2 sensor(s)?Are they heated? Is it wide band? Can you tell if you're in mixture closed loop mode?My much older PCM (EDU) is nowhere as smart as yours.When my in-tank low-pressure fuel pump (there's no high on TBI) was dying, the engine would be gasping but no codes.I added detection for lean and rich to pop up on the display.I only have a narrow band O2 so it just crosses constantly.I got another month of usage out of my dying fuel pump by knowing not to push it when it was leaning out.But your problem is either too rich or bad combustion due to

author: SilverSolder
author_rank: Super Contributor
timestamp: November 13, 2020, 06:10:29 pm
content: Quote from: ssashton on November 13, 2020, 05:21:52 pmYeah, I hate not being able to trust my readings too - in this case, it is a huge handicap. Maybe sanity check the OBDII readings with a phone app (I use OBDFusion but there are many), and a cheap Elm compatible dongle? Sometimes local parts stores have readers they will let customers use (or even read the customers' cars for them) hoping to sell parts, obviously.... Or maybe take it by a local mechanic with a "serious" reader to cross check your readings? Sometimes ECMs have extended trouble codes available that go beyond OBDII, but you need a tool that knows the vehicle specific codes to "see" them; typically a mechanic will have tools that can do that.Obviously it would help enormously to narrow it down to cylinders 1 and 2 like your tool suggests, OR confirm that it happens across all of them (there is an OBDII code for that, too).If it really affects only cyls 1 and 2, it is probably something mechanical or a leak, given all the parts you've already swapped. If it is all of the cylinders, the next suspects are as @fcb suggested, the crankshaft sensor and the MAF, and also the O2 sensor. One of the ways that an O2 sensor can fail is to send a false signal to the ECM which causes an incorrect air/fuel mixture.

author: ssashton
author_rank: Frequent Contributor
timestamp: November 13, 2020, 06:14:38 pm
content: I tried un-plugging both O2 sensors and it made no difference.I did the leak-down test. I also removed the intake manifold so I could listen better for the location of leaks. I can't remove the exhaust manifold without extensive work so left it on.First I had a look at the intake valves which are quite dirty, but that is normal for this engine. However I realised something - some of them looked wetter with more carbon built up around the stem, while others looked dryer especially around the valve head. If the valve stem seals were bad it would be sucked down the valve stem and be concentrated around there. Or... it could be oil vapour from the crankcase ventilation which gets sucked in to the intake as it's supposed to do, but then I'd expect it to be all over the valves, not concentrated around the stem. Right?Here are the leak-down results. Pressure was only 15psi which seems low to me, but I bought a second tester from Sealey and that was the same so I guess it's the norm.I tested each cylinder twice, rotating the engine between tests. On one occasion I clearly hear leaking from C3 inlet valves. During the other tests it was very difficult to hear the location of leaks. I did note that C1 with minimal leakage was quieter! The variation between each test suggests valves though, I think?

author: bdunham7
author_rank: Super Contributor
timestamp: November 13, 2020, 06:35:05 pm
content: Quote from: ssashton on November 13, 2020, 06:14:38 pmInlet valves are the place where an engine has the least tolerance for leakage (except perhaps into the cooling jacket). You can increase the pressure to try and pinpoint the leakage, or you can put a small amount of solvent in the ports and see if it bubbles, but if you have clearly noticeable leakage from any inlet valves you have identified a problem that needs fixing before you can even hope to have an engine that operates correctly. Those valves look absolutely awful. GDI + EGR + PCV = TAR.

author: fordem
author_rank: Regular Contributor
timestamp: November 13, 2020, 06:38:18 pm
content: Assuming the compression test was properly done - all plugs removed, engine warm, battery fully charged, throttle plate wide open - if the engine returns good wet & dry compression numbers, there is no need to do a leak down test.

author: drussell
author_rank: Super Contributor
timestamp: November 13, 2020, 06:55:39 pm
content: Ah, geez, those intake ports look brutal!If it were me (I have various valve-spring compressor tools including the big C-clamp style,) as a matter of principle I would pull the head, disassemble, clean and test everything and install at least new valve stem seals but looks like it probably needs guides too if it's leaking that much oil.Wow! No wonder those engines have issues!

author: drussell
author_rank: Super Contributor
timestamp: November 13, 2020, 06:58:20 pm
content: How many km are on that thing, anyway?

author: Renate
author_rank: Super Contributor
timestamp: November 13, 2020, 07:28:25 pm
content: Wow, those valves look filthy!Some new valve seals seem to me a good idea.OTOH, the plugs aren't oil fouled, are they?Would leakage on the intake valves cause such incomplete combustion?Is such incomplete combustion visible as a short burn time on the ignition scope?Disclaimer: I know some things about some things and nothing about many things.I'm just mixing it up here to learn something.Isn't that why we're here?

author: bdunham7
author_rank: Super Contributor
timestamp: November 13, 2020, 07:53:34 pm
content: Quote from: Renate on November 13, 2020, 07:28:25 pmIntake valve leaks are especially problematic because they allow inert (or at least deoxygenated) combustion gases to displace the air in the intake manifold. This causes poor combustion in other cylinders and also can cause the ECU to miscalculate the required fuel. Those valves deposits are probably not caused by excessive oil, but rather a nasty combination of exhaust and crankcase gases settling out on the relatively cold intake valves. On engines with a separate EGR valve, those deposits are often found throughout the intake system and can be quite a mess. If EGR is accomplished with valve timing, the intake valves may get the worst of it. The problem is compounded in GDI engines because there is no fuel spray to clean off the valves.

author: ssashton
author_rank: Frequent Contributor
timestamp: November 13, 2020, 08:00:43 pm
content: Engine on about 50K. Unless a previous owner messed about with the oedometer. The body of the car certainly looks like 50k, nice and tidy. However the engine obviously doesn't work great!Spark plugs are black but not wet.These engines are famous (infamous) for drinking oil. Not only do they have crankcase ventilation going though the intake manifold without port injection to keep the valves clean, they also have a higher than standard running temp of 110C, which I guess means they are more leaky when cold.You can do in-situ valve cleaning by walnut media blasting. However this is done with the valves shut so not going to clean the actual sealing surface and not offered for exhaust valves.There is no EGR porting evident, so I assumed it just doesn't do EGR. Maybe as suggested above it is accomplished by exhausting a little out the intake valve? I never thought of that.

author: SilverSolder
author_rank: Super Contributor
timestamp: November 13, 2020, 08:39:35 pm
content: The intake valves will get dirtier with a GDI engine, which doesn't have a "petrol shower" to keep them clean... this is a known issue. That said, I have seen worse carbon coated valves than yours on engines that ran OK...There are a couple of defensive moves you can make once you get it all going: you can add an inline catch can/separator/filter to the PVC line, and you can use synthetic oil which is more stable and should reduce the amount of vapours hitting the hot valves.Pretty much all gasoline engines use EGR to buffer the combustion and reduce pollution - the EGR valve is built into the head on some engines, I'm not familiar with the Mini.The leakage numbers do look a little on the high side, but it is hard to envision how it would cause a misfire that appeared relatively suddenly on multiple cylinders.Might be worth eliminating a potentially glitchy crankshaft or camshaft sensor, or an incorrectly reading MAF sensor, from the list of suspects?

author: Renate
author_rank: Super Contributor
timestamp: November 13, 2020, 08:47:22 pm
content: Quote from: bdunham7 on November 13, 2020, 07:53:34 pmI've got TBI, I wash my intake valves.

author: bdunham7
author_rank: Super Contributor
timestamp: November 13, 2020, 08:47:51 pm
content: Quote from: ssashton on November 13, 2020, 08:00:43 pmIt doesn't have to vent back to the intake manifold, it simply has to retain some exhaust in the cylinder. This reduction in scavenging efficiency can be implemented in software once you have variable cam timing.

author: maginnovision
author_rank: Super Contributor
timestamp: November 13, 2020, 10:25:03 pm
content: Those engines are not good. Even under warranty they were replaced way too often. I'd start by cleaning the valves and re-checking. The way your valves look is not abnormal for that engine.

author: ssashton
author_rank: Frequent Contributor
timestamp: November 14, 2020, 05:47:10 pm
content: I've started on disassembly to remove the head. God help me, lol! Looks like a huge job, but thankfully Eric The Car Guy has done it on video.I didn't see any valve seals in Eric's video. Do some engines not have them and rely only on a tight fitting stem guide?

author: Johnny10
author_rank: Frequent Contributor
timestamp: November 14, 2020, 06:05:01 pm
content: Ahhh,I remember it well.... down down the rabbit hole we go.To replace the engine in the car I was working on $1200.00After deciding to solve the misfire problem myself, I purchased a total of $3400 in test equipment and started my test equipment hobby.And look at me now!Test Equipment Junkie

author: bdunham7
author_rank: Super Contributor
timestamp: November 14, 2020, 06:17:04 pm
content: Quote from: ssashton on November 14, 2020, 05:47:10 pmThat guy seems to be a somewhat knowledgeable hack--but still a hack--and that engine didn't sound so good at the end. I'd recommend you find an actual service manualThere are examples of older engines that didn't have positive valve seals on the exhaust, or even more ancient engines without positive valve seals at all, but your Mini assuredly has them. Look closely at 30:01 on the first video. They appear to be the type that has the seal and the valve spring washer combined. Apparently he didn't bother replacing them.

author: drussell
author_rank: Super Contributor
timestamp: November 14, 2020, 06:40:05 pm
content: Quote from: Johnny10 on November 14, 2020, 06:05:01 pmYep, that's what the TEA thread is for....It is bound to either help you, or hinder your recovery depending on what "stage" you're at??

author: ssashton
author_rank: Frequent Contributor
timestamp: November 21, 2020, 05:16:38 pm
content: All things going as planned (lol) I should get the head off tomorrow. I'm just focusing on each task in front of my nose and trying not to think about the work needed to re-attach all the bits!I plan to change all valve stem seals, which is something I've never done before. Is there anything method to it, other than taking off the spring, pulling off the seal and placing a new one? Any specific procedure I need to note?Also, I wasn't planning to change the valve guides. They are expensive! Is there anything I should look for specifically to tell if they are worn? Valve wobble?Thanks!

author: drussell
author_rank: Super Contributor
timestamp: November 21, 2020, 06:42:06 pm
content: Quote from: ssashton on November 21, 2020, 05:16:38 pmNope, that's pretty much it... On most engines, you just need an appropriate valve spring compressor to be able to smoosh down the spring and retainer so you can pop out the keepers. Once the spring is out of the way, on most engines the valve stem seal is just a little rubber hat that you can pry off of the top of the valve guide, clean everything up, then push on the new ones (with somegoodquality break-in lube slathered on everything underneath, of course!)I still prefer a good, old-school molybdenum-disulfide-based break-in lube, but some RedLine, or even just some of the old LubriPlate 212 or whatever it was should work fine if that's all you have. I just really like the fact that i can pull my heads off after a year or two and still see the traces of moly in there on my workhorse engines.... YMMVQuoteIf your valves wobble noticeablyat allin the guides, then they are well past the "worn-out" phase, even without doing the proper individual measurements of the stems and guides. You could at least check the valve stems for wear, but it's highly likely that any wear is in the soft guides instead of the hard stems, but it's always worth a look. If you stick your finger over the top of the guide, you should build suction/pressure as you push the valve up and down from the cylinder side (when clean and dry, no lube...) If it leaks significantly and doesn't pressure up, you need to take the head to an automotive machine shop and have them put in new guides, then (on most engines) re-grind the seats to be concentric with the new guides... They'll alsoalwaysre-grind the valves and set the heights properly for you if they're a competent machine shop.None of my engines have replaceable guides (they're pretty much all just cast iron heads), so I always have the machine shop install phosphor-bronze inserts and then ream to size. This results in a set-up that isfarmore durable than what came from the factory! DoNOTlet some cut-rate shop talk you into knurling the guides to restore the clearance. That will actuallyincreasethe oil consumption, and by the sounds of your engine style, that's thelastthing you want to do.It is probably mostly bad seals, but you really never know what is going on until you get in there, hence the reason for actually pulling the head and doing a bit of sleuthing....Edit:to fix typos and also to say, about a valve job:"It's not at alldifficult, it's just very a labour intensive and time consuming task..."

author: jonpaul
author_rank: Super Contributor
timestamp: November 21, 2020, 07:18:33 pm
content: Can we please move this entire topic to a CAR FORUM and stop using EEV blog for a car repair?Jon

author: SilverSolder
author_rank: Super Contributor
timestamp: November 21, 2020, 07:30:13 pm
content: Quote from: jonpaul on November 21, 2020, 07:18:33 pmWhy would electronic ignition systems, engine management systems, and so on, not be relevant to electronics enthusiasts??If you are not interested in that type of electronics - skip the topic?

author: bdunham7
author_rank: Super Contributor
timestamp: November 21, 2020, 07:42:01 pm
content: Quote from: ssashton on November 21, 2020, 05:16:38 pmThere are special tools for removing and installing valve seals, but on those 'hat' types, they're pretty easy to press back on. Use a socket that fits if you need to.The guides can be inspected visually to see if they are scored or using a dial gauge to see if there is more movement in one direction than another. If there is wear, it is typically in one direction, so the guide will be oval at the bottom and the valve will move more in the direction perpendicular to the camshaft and less in the direction parallel to it. I'll be surprised if you have any real issues with guides or seals.

author: drussell
author_rank: Super Contributor
timestamp: November 21, 2020, 07:44:45 pm
content: Quote from: jonpaul on November 21, 2020, 07:18:33 pmIs someone somehowforcingyou to read this thread?!You're welcome to just go follow the blinkenlights threads in Beginners if you want pure modern MCU "electronics" and stuff, nobody is dragging you in here (I hope)....Some of us are trying to just actually make our stuff keep running, even if it ends up veering a little bit off "topic!"

author: John B
author_rank: Frequent Contributor
timestamp: November 21, 2020, 08:46:46 pm
content: I'm working on a related problem where I need to scope the timing between injectors and ignition, but in a way that I can safely hook up my $2.5k scope. The injector wire on the ECU is sinking the full current, so in this case around 1.9A, but the ignition wires are connected to coil on plug setups with an inbuilt "igniter" so I assume that the ECU current is low.I was thinking either making an inductive pickup with a split core ferrite EMI filter with a bunch of secondary turns to make a rudimentary transformer or maybe just a bunch of wire coiled around an ECU signal wire for capacitive coupling?

author: bdunham7
author_rank: Super Contributor
timestamp: November 21, 2020, 08:57:03 pm
content: Quote from: John B on November 21, 2020, 08:46:46 pmAn ordinary scope should be fine with these signals if you use a standard 10X probe. If you are extra nervous and will be scoping actual primary ignition signals, you can use a 100X/10M probe like the Probemaster 4910-2.

author: John B
author_rank: Frequent Contributor
timestamp: November 21, 2020, 09:21:45 pm
content: The other issue is that it's difficult to actually get a metal to metal contact point without having to manually hold a probe. The back of the ECU block connector is accessible, but you have to poke a DMM style probe tip into the pin sockets.

author: bdunham7
author_rank: Super Contributor
timestamp: November 21, 2020, 10:31:58 pm
content: Quote from: John B on November 21, 2020, 09:21:45 pmThere are all types of backprobes for those connectors, even a small paperclip will do. Just insulate where needed, install them in the connector and clip onto them with the probe test hooks.

author: ssashton
author_rank: Frequent Contributor
timestamp: November 21, 2020, 11:00:53 pm
content: Quote from: drussell on November 21, 2020, 06:42:06 pmThat's great advice, thank you! I think the BMW N14 engine in mine has replaceable guides as I googled and saw bronze sets of 16.Quote from: bdunham7Again good advice, thank you!Quote from: John BMy injectors have reasonably large connection pins. So it was easy to get some small crocodile clips on the back and hook them up to the plug with some T pins. Then I was able to probe easily off the T-pin. I could access C1 and C4 injector plugs from the sides but C2 and C3 are hidden below the intake manifold.You can see here how I simply have crock clips in the injector when I had it set up for pattern testing.DIY Injector Testing

author: ssashton
author_rank: Frequent Contributor
timestamp: November 24, 2020, 01:48:49 pm
content: I know this is purely mechanical, not electronics but I feel the story should play out!Got the head off. There seems to be some molten metal on my exhaust valves and a little on the head.What the hell can it be?!I'm not sure if this happened during my ownership. The car was an insurance write-off but got repaired, passed safety tests and this sucker herebought it cheap thinking he got a bargain.At first I thought it was a plating that got burned off, but I don't see anything like that on google images. Also I don't think they are sodium filled valves that have leaked, as you can buy sodium filled ones as expensive upgrades.Oh, also I notice the cup in the intake valves is not exactly central. However, they do not all appear to be positioned in the same direction in my engine. Why is it like that and should they be in a specific orientation?

author: ssashton
author_rank: Frequent Contributor
timestamp: November 24, 2020, 01:53:47 pm
content: P.S. No sign of problems in the engine block.

author: fcb
author_rank: Super Contributor
timestamp: November 24, 2020, 02:00:10 pm
content: That doesn't look like molten metal - just normal carbon deposits on a high-miler. You can test it if you can get some decoking fluid (CCL4 - carbon tetrochloride unless it's banned now) - brake cleaner might work also.The valve appearing not centred is just manufacturing tolerance, the body of the valve is cast or forged and then important surfaces subsequently machined, that dipped surface is likely just the raw blank.

author: ssashton
author_rank: Frequent Contributor
timestamp: November 24, 2020, 02:09:29 pm
content: The deposit will not scratch away even with a hardened steel metal punch. Looks metallic under the black dirt, too.

author: drussell
author_rank: Super Contributor
timestamp: November 24, 2020, 02:53:00 pm
content: Quote from: ssashton on November 24, 2020, 01:48:49 pmThanks for updating, I hate it when people run off any we don't get to find out what happened!That just looks like carbon buildup. A wire wheel in a drill or die grinder or something is usually all I use to get it all off. Since your head is aluminum, be sure not to gouge into it as you clean things off. The tops of the valves (where the air rushes by, on the port side, where the stem is) are probably pretty badly coked up if the combustion chamber side has that much buildup. It will probably take some gooood brushin' to get it all off. Some Super Clean or Spay Nine or something might help out (even soak them in some for a couple hours) on the valves but I wouldn't use more than a quick spray here and there on the combustion chambers before rinsing as it will be quite reactive with the aluminum and you don't want to start pitting things. The chambers don't have to beperfectbut you should be able to get most of it off with a wire wheel, and the valves should actually clean up 100% without insane effort. I use a wire wheel mounted in my drill press for cleaning valves.QuoteAs noted above, that just looks like manufacturing tolerance. Don't worry about it, the valves will always spin a little bit in operation. The exhaust valves on some engines intentionally have little bearings in the retainers to rotate the exhaust valves to reduce wear (or at least even it out.)

author: drussell
author_rank: Super Contributor
timestamp: November 24, 2020, 02:59:09 pm
content: Quote from: fcb on November 24, 2020, 02:00:10 pmCarbon tet is banned pretty much everywhere, but mechanical action with a wire wheel will break that stuff off relatively "easily." It can be pretty stubborn, though. Been there, done that!Quote from: ssashton on November 24, 2020, 02:09:29 pmOh, it will come off... It might try to fight you, but itwillcome off!Like I said, try a (steel) wire wheel. It will take a fair bit of pressure on the valves to kinda grind it off, which is why I usually mount the wheel in my drill press then be able to really get a good grasp on the valve and manipulate it around and really mash it into the wheel where the carbon is on the face and on the back between the stem and where it contacts the seat. That radiused area on the intakes is usually where the most buildup is, at least onmyengines.

author: SilverSolder
author_rank: Super Contributor
timestamp: November 24, 2020, 03:04:20 pm
content: Quote from: ssashton on November 24, 2020, 02:09:29 pmIt's carbon, with 99 44/100 percent certainty.It can harden really well in the heat and pressure.

author: bdunham7
author_rank: Super Contributor
timestamp: November 24, 2020, 03:14:13 pm
content: Quote from: ssashton on November 24, 2020, 02:09:29 pmThe exhaust side deposits are typically from organometallic compounds in fuel and oil additives, the residue is likely mostly a manganese-iron alloy or something like that. On a low-mile engine this indicates a lot of city driving--low speeds and temperatures. You won't be able to remove it from the valves by anything short of grinding. The deposits in the head may be removed by bead blasting, but you need to completely disassemble and prep the cylinder head to do this, otherwise you'll have blasting media in nooks and crannies that will cause trouble later. If you are strictly DIY, then some careful grinding with a small dremel tool may be sufficient.The valve eccentricity you notice is because the valves are two-piece friction welded type and they rely on the final machining to get the important dimensions correct. They probably cost the OEM less than a buck a pop, although you won't see them for that price.

author: drussell
author_rank: Super Contributor
timestamp: November 24, 2020, 03:30:42 pm
content: Quote from: bdunham7 on November 24, 2020, 03:14:13 pmYeah, the backs of the exhaust valves tend to have brownish-tinged additive deposits on them rather than carbon, since they get blasted like a blowtorch, but it's usually just mostly a thin layer and it doesn't really have to be perfect. Theintakeside though, and the valve faces should just be very stubborn carbon (coke) caked on them and should come off. Same for the combustion chamber itself. For cleaning the chamber, my suggestion is to leave the valves in there to help protect the seats while you brush, then once you're done, remove the valves and clean them separately as described above. Ending up lightly polishing the combustion chambers is actually desirable, you just don't want to start really gouging into the aluminum.I have a heating element out of an old coffee pot that I use basically just for cleaning valves. I stick an old metal-type coffee can with some SuperClean in it on there and let the valves sit overnight in the warm NaOH... Makes it easier to grind off with the wheel. Interestingly, it always seemed that if I let them soak for the night in the warm bath, then took them out and left them open to air for a day, it would get even easier for some reason, but that might just have been the particular deposits on the particular engine or something, since I'm not sure of the chemistry of how it would have that effect.Quote from: fcb on November 24, 2020, 02:00:10 pmQuote from: bdunham7 on November 24, 2020, 03:14:13 pmYeah, I meant to mention that it sure does look like a lot more than 50k on that engine by the look of the deposits so I see where these engines get their reputations as carbon-buildup-machines.It will be interesting to see whether the valve stem seals still seem pliable and "sealy" or not and what shape the guides are in (especially the intakes, since that's the side that will "suck" oil in.

author: ssashton
author_rank: Frequent Contributor
timestamp: November 24, 2020, 03:42:03 pm
content: The intake valves seem to clean up easily. I've got the back sides soaking in petrol right now, waiting for the valve spring compressor to arrive.I'm not very confident about cleaning those exhaust valves without damaging the sealing face. I've just ordered a new set.Since I have a new set coming, I'll try to break off a bit of the deposit and get it under the microscope.

author: drussell
author_rank: Super Contributor
timestamp: November 24, 2020, 03:55:43 pm
content: Quote from: ssashton on November 24, 2020, 03:42:03 pmYou may find that the edge of the exhaust valves' face (where it contacts the seat, the beveled sealing portion) is already starting to pit and erode anyway, in which case new valves aren't a bad idea as they would theoretically need to be reground anyway to be "proper." On the other hand, if it is just a bit of deposit but they seal properly, it wouldn't matter, but if they're reasonably priced, why not?When you're done cleaning up and re-assemble everything, install the spark plugs, prop the head up with the combustion chamber up and fill it with solvent. If any leaks past the closed valves under their normal spring pressure, you have valve sealing problems that need to be corrected before you put the head back on the engine and could require a trip to the machine shop rather than a quick lapping-in, but if the seats look good and the valves look good, you're probably golden!If you do lap your valves, my trick is instead of using one of those rubber suction-cuppy things, I put the compound on, put a little lube on the stem, stick it in the head and then chuck the valve stem into a drill on low speed and just pull up a couple times to swirl it around. Polishes them up nicely on a head that didn't require a trip to the machine shop.I've had the heads off the van at least four or five times over the years and they've only been to the machine shop once (to install the phosphor-bronze guide inserts and re-grind the intake seats for 2.02" valves instead of the stock 1.88".) Every other time, I just clean them up, do a quick lap-in, and put 'em right back into heavy-duty severe service. (Well, not counting time spent on the bench with a die grinder doing more and more extreme porting and whatnot...)

author: ssashton
author_rank: Frequent Contributor
timestamp: November 24, 2020, 04:19:13 pm
content: Scrapped back some of the deposit with a knife. Looks like sand, kind of yellow white.It came off more as powder than chunks so couldn't get a piece under the microscope.Strange thing is, cylinder 2 has none, despite still having nasty intake valves like the rest. If this were oil/addatives from the intake side, I'd expect to see it on C3 as well... Same with fuel deposits. Hmm..This is C2.

author: drussell
author_rank: Super Contributor
timestamp: November 24, 2020, 06:12:09 pm
content: Quote from: ssashton on November 24, 2020, 04:19:13 pmYes, that is totally the same as my typical experience with the hundreds of exhaust valves I've cleaned over the years. Obviously the deposits may be slightly different, changing over the years depending on gasoline additive formulations, geographical location where the fuel was mixed, etc. but that looks pretty much exactly like I would expect. Most of thatdoesfairly easily wire wheel off though, surprisingly, just FYI.QuoteThisis why it is invaluable to actually lookinsidethe engine. You can do the forensics (even when it's just "routine maintenance" and not afailure, per se) and see what is really going oninsidethe engine. You cannot diagnose these kinds of things from outside the engine. That's why I've always pulled the heads off the van once or twice a decade...I will be very curious to see what your seals and valve guides look like once you've inspected them! That is a lot of carbon and apparently the deposits are not evenly distributed between cylinders, which is abnormal... It will be interesting to see where the differences lie, especially since this is direct injected... I've never worked on one of those before, but that doesn't seem like it (a single bad injector or something) would account for theextracarbon on the other cylinders... Even if cyl 2 is constantly being washed down by extra gas somehow or something, that really doesn't explain everything, IMHO....Keep up the good work, for your first time (?) into the top end of an engine, it seems like you're doing all the right stuff!!

author: drussell
author_rank: Super Contributor
timestamp: November 24, 2020, 06:25:33 pm
content: Oh, also, something I hadn't mentioned!Inspect very closely (especially around the exhaust valve seats, on your 4V engine, particularly that short path BETWEEN the exhaust valves,) for cracks! Yours will have hardened seatinsertssince it is an aluminum head, so very carefully inspect the seats for cracks! If you have access to one of those dye penetrant kits, USE IT!One of my original 1978 heads was cracked between the (2V) intake and exhaust when the machine shop magnafluxed it. Had to go to the junkyard and find a couple spares so one of the ones on the van is not technically the original anymore... hahaI haven't pulled the heads off since the late 90s, it'sWAYoverdue for another inspection.(Mopar Performance doesn't still sell the super-thin (.022-.024 crushed-thickness) head gaskets that I run though, and I used the last spare set I had the last time I pulled them, so I need to find an alternative to keep my compression ratio up where I want it with those half-thickness gaskets... Supposedly Mr.Gasket still makes them, and were supposedly the ones sold by MP, just colored red for the MP version or something... Going to have to look that up...)

author: SilverSolder
author_rank: Super Contributor
timestamp: November 24, 2020, 10:12:17 pm
content: Quote from: drussell on November 24, 2020, 06:25:33 pmNot possible to skim that thickness off the heads?

author: ssashton
author_rank: Frequent Contributor
timestamp: November 25, 2020, 04:20:13 pm
content: Thanks for all the tips and the encouragement!It is the first time I've taken the head off before, so even though I am stressed about my car not working it's also rather interesting for me!Looking forward to the spring compressor arriving one of these days lol. So much for the eBay seller being in the UK, cheeky beggars.If the engine still won't run well once re-assembled I'll be back looking at scoping the ECU lines.

author: ssashton
author_rank: Frequent Contributor
timestamp: November 29, 2020, 03:45:08 pm
content: One of you mentioned the valve guides. What do you think about this?Number 6 wobbles the most. I haven't checked the exhaust yet.Valve guides are not expensive but I gather you need to use temperature differential to get them in and out. Sounds like I could ruin my head if I try that at home.https://photos.app.goo.gl/Htyz97hKpSZspwjEA

author: bdunham7
author_rank: Super Contributor
timestamp: November 29, 2020, 04:01:06 pm
content: Does the valve (especially your #6) move a lot more up/down than from side to side? I don't know the specs for that engine, but that doesn't look good at all. I said I'd be surprised, and so I am, especially given the low miles on the car.Replacing the guides usually involves remachining the seats for concentricity and is a machine shop job unless you get quite lucky. At this point you might want to price out a remanufactured exchange cylinder head assembly.

author: CJay
author_rank: Super Contributor
timestamp: November 29, 2020, 04:22:37 pm
content: Quote from: ssashton on November 11, 2020, 01:32:47 pmPicoscope specifically target the automotive diagnostics market with their USB scopes and have a *lot* of accrued knowledge on the subject, they even publish training info that shows you how to diagnose various faulty bits on your car.https://www.picoauto.com/library

author: ssashton
author_rank: Frequent Contributor
timestamp: November 29, 2020, 05:56:25 pm
content: It does move slightly more up and down then left to right. I'll go stick a dial indicator on it now and find out.I'm starting to think a previous owner swapped the engine, but kept the ECU bits. So the ECU would say 50K but the engine might be on much more!The cam bearings have scoring on them so I guess it was run low on oil at some point (common on this engine as they drink oil and owners who don't know that might not check regularly).The valve guides are manganese bronze inserts so I would think there should be no need to machining just to replace those? Of course getting them out and new ones back in without damage is the trick.I'm not sure I'll bother, since I'm not building a race car, just trying to get my daily working again!

author: SilverSolder
author_rank: Super Contributor
timestamp: November 29, 2020, 06:16:12 pm
content: Quote from: ssashton on November 29, 2020, 03:45:08 pmThat is definitely way, way too much movement - the acceptable lateral movement is at the thousandths of an inch level. Well done for persevering with taking the engine apart enough to spot this! I agree with you that it has probably run low on oil. Maybe have a look to see if you can get a low mileage engine from an auto recycler? Could be cheapest/best solution overall!

author: drussell
author_rank: Super Contributor
timestamp: November 29, 2020, 07:23:41 pm
content: Quote from: ssashton on November 29, 2020, 03:45:08 pmOh, wow... No, that isWAYpast being worn out. That engine will never run properly like that.Yeah, unfortunately for you, I figured it wasn't just seals, I suspected severely worn guides all along.Was the compression still good, like is the bottom end probably OK? If so, take the head to a competent machine shop and have them replace the guides and regrind the seats for you. The stock valve guides may only be cast iron, get the bronze replacements or do inserts. Don't let them talk you into knurling or replacing with new stock-style cast iron guides if that's what the factory had in there.I highly doubt this engine has only 50K km on it, it must have been swapped out or your mileage has been altered. Does the serial number on the block match the VIN? I kinda doubt it is the original engine.QuoteThey're normally just pressed in but I do not know the specifics on this engine.Regardless, when you change the guides you need to have the seats re-ground to be concentric with the new guides, unless you have the tooling to regrind valve seats at home, this is a machine-shop-only operation. Seek out agoodshop in your area. It likely won't be cheap but in the long run a valve job is actually affordable.Before you take it in, clean up the bowls and ports with a die grinder or dremel, just smooth things out, don't go crazy on "porting" your heads, just do the "rest" of the machine work that the factory leaves as bare casting through the ports to under the valves. Just polishing everything up makes a noticable difference in performance and it only takes a little time and a couple grinding stones and mini flap-discs (or better yet, a carbide cutter!!)That head is completely useless as is.Either re-man the one you have or do an over-the-counter swap on a rebuilt head if that is available in your area at a reasonable price.(Also thoroughly inspect everything else on that engine, though... Luckily your cylinder bores DO look pretty good from the cursory glance I took at an earlier photo, although I don't really see major remnants of the honing crosshatch. My van engine at 200,000 km still had visible factory crosshatch the first time I rebuilt it, just a little tiny bit of taper and wear at the very top and bottom so decided to bore it anyway so I had two matching engines with identical parts... YMMV)

author: drussell
author_rank: Super Contributor
timestamp: November 29, 2020, 07:34:04 pm
content: Quote from: ssashton on November 29, 2020, 05:56:25 pmAny noticiable movement will be WAY out of spec. The valve will never seal properly and it will drink oil. It's done. You need at least a valve job. Period. Don't try to shortcut it, you'll just be wasting time and money.QuoteQuite possible.QuoteAlso quote possible. Cam bearings don't need to be perfect but it is an excellent indicator of either horrible abuse or a swapped-in higher-mileage engine.QuoteYou can replace them at home but the seats stillmustbe reground to be concentric with the new guides. I don't think you're likely to be able to just lap them in unless the manufacturing tolerances are down totenthsof thousands of an inch. The valves must seal perfectly or you will have misfires and such like you had to start with, it will backfire up into the intake port, etc. This would absolutely, certainly cause misfires and issues like you were seeing before. It's toast.QuoteThere's no choice on this one... You cannot get away without changing the guides. Those ones arecompletelyfuckered. You need a valve job. No ifs ands or buts.

author: bdunham7
author_rank: Super Contributor
timestamp: November 29, 2020, 07:55:10 pm
content: Quote from: drussell on November 29, 2020, 07:34:04 pmThere is always 'noticeable' movement of the valves on this type of engine when you pull them out an inch and wiggle them, as the clearance is greatly magnified. You need to actually look up the measurement method and spec and go by that. My question about side-to-side vs up/down address this without getting too technical. If they are the same, there is likely no wear.

author: drussell
author_rank: Super Contributor
timestamp: November 29, 2020, 08:23:02 pm
content: Quote from: bdunham7 on November 29, 2020, 07:55:10 pmOk, whatever...The wobble evident in that video will NOT work satisfactorily, even for regular, stock street use. Period.I've personally built dozens of engines. I don't care what the spec technically is on that particular engine, I have no experience with that model, but that valvetrain is shot. If the OP re-assembles that engine as-is, it will NOT work properly. Guaranteed.

author: bdunham7
author_rank: Super Contributor
timestamp: November 29, 2020, 08:37:21 pm
content: Quote from: drussell on November 29, 2020, 08:23:02 pmI owned and operated a production engine manufacturing and machine shop and at last count we had built over 14,000 engines over 30+ years, in addition to a great deal of machine work for other shops and dealers. That included machine work for warranty repairs for those OEMs that permitted it (some, like Chrysler, didn't). I always cared a great deal what the spec was on a particular engine. Not everything is a small block Chevy.

author: ssashton
author_rank: Frequent Contributor
timestamp: November 29, 2020, 08:54:35 pm
content: Guys both your info is greatly appreciated!I've done some measurements with a dial indicator, valves at about 30mm extension.Side to side movement on all valves is 0.2-0.25mm 'peak to peak'. As suggested this is probably close to the un-worn spec.Up and down movement is: 0.4mm on all valves, except valve 6 which is 0.6mm.Exhaust valves not tested yet, but I will.As the guides are bronze insert types, would the valve seats still need re-machining? If you hadn't said otherwise, my assumption would have been the valve guides are precision machined parts that will be perfectly concentric to the receiving bore in the ali head.

author: bdunham7
author_rank: Super Contributor
timestamp: November 29, 2020, 09:14:33 pm
content: Quote from: ssashton on November 29, 2020, 08:54:35 pmThat's not good, but it will probably run. I would consider it unacceptable for reuse unless your available time to available cash ratio is exceptionally high.The issue with the valve guides depends on the manufacturing process and the replacement guides. For remanufacturing, typically the valve guides are replaced first, and if they come blank or semi-finished, they are then bored to size. Then the valve seats are cut using a machine with a pilot that uses the fresh valve guide as a reference. OEM CNC machining practices are very advanced, so on modern engines it is possible in some cases that both the original and replacement valve guides will be perfectly concentric and a replacement can be made without altering the location or orientation of the valve. However, all that would have to be carefully checked for each valve and given what I'm seeing in your case, I'm not optimistic that you will get away without any valve seat machining. For one thing, there's probably some wear on the #6 valve seat.How bad are those cam caps? Can you post a photo?And, let's not overlook the obvious. Can you measure the valve stems with a micrometer? Or move the #6 valve temporarily to a different guide and check again?

author: ssashton
author_rank: Frequent Contributor
timestamp: November 29, 2020, 09:50:19 pm
content: I found one supplier who specs the valve guide internal diameter as 5.01mm. The valve stems are 5mm.A quick bit of autocad tells me that would be movement of about 0.05mm at the extension I had the valves. So a factor of 10 worse in my engine.That said the spec on the site might be rubbish. Won't the valves just bind like an interference fit?

author: SilverSolder
author_rank: Super Contributor
timestamp: November 29, 2020, 09:56:22 pm
content: A quick Google consultation (ok, Bing actually) found that worn out valve guides is a common problem with Mini Cooper cylinder heads?A set of guides is only $50... so changing them doesn't seem to be a world-ending thing, all you'd need then is for a machine shop to cut the seats if necessary. I haven't worked on thousands of engines or anything, but I have never seen a valve move as much as what you showed in the video - even before restoring the head with new guides!This article on guide wear seems very comprehensive, and it even claims it can be a cause of rough idling etc. -https://www.enginebuildermag.com/2003/12/valve-guide-reconditioning/

author: bdunham7
author_rank: Super Contributor
timestamp: November 29, 2020, 10:01:14 pm
content: Quote from: ssashton on November 29, 2020, 09:50:19 pm.01mm would be way too tight even for intakes. I couldn't find a spec off-hand for the N14, but for the earlier Mini engine (with 6mm valve stems) I found a spec that listed the maximum valve guide clearance for inlet as 0.076mm and exhaust 0.101mm. I would have guessed that 0.05mm (.002" in my world) would be somewhat typical. I suspect your specs are in this range.Those caps look ugly. Are the ridges big enough to catch your fingernail? And what do the cams look like?

author: SilverSolder
author_rank: Super Contributor
timestamp: November 29, 2020, 10:11:46 pm
content: Quote from: bdunham7 on November 29, 2020, 10:01:14 pmThat fits my limited experience, and would make the OP's measurement of 0.2-0.25mm about 4x - 5x too "sloppy".Maybe the worn guides helps explain the large amounts of oil/carbon found on the back of the intake valves?

author: ssashton
author_rank: Frequent Contributor
timestamp: November 29, 2020, 10:16:24 pm
content: The cost of the guides are not a problem, I can get OE parts for £2.80 each. It's the cost of the machine shop that worries me! I've sent out some enquiries though.The cams don't look bad at all, very smooth and shiny. It's only the bearing parts that look nasty. There are a few ridges that I can feel, but most not. Either way I doubt that is what stopped it from running well. If the cams were re-ground at the machine shop, would I then need 'inserts' on the bearings to make up the clearance?

author: bdunham7
author_rank: Super Contributor
timestamp: November 29, 2020, 10:20:17 pm
content: Quote from: SilverSolder on November 29, 2020, 10:11:46 pmNo, pulling the valve out like that geometrically magnifies the clearance by several times, 4X if you pull it out exactly the effective guide length less any counterbore.The seals are what determine whether oil gets through, not the guide clearance--especially the guide clearance at the bottom of the guide. If his seals aren't cracked or brittle, they likely weren't leaking.

author: bdunham7
author_rank: Super Contributor
timestamp: November 29, 2020, 10:23:43 pm
content: Quote from: ssashton on November 29, 2020, 10:16:24 pmI'm not aware of any camshaft inserts being available, most heads like this are disposable if the cam bearings are ruined. For some popular heads there are kits to rebore the cam bearings back to standard after you cut the caps. If you can't catch a fingernail on the ridges, then most likely that is the least of your problems.

author: ssashton
author_rank: Frequent Contributor
timestamp: November 29, 2020, 11:10:27 pm
content: Found this for the similar N16 engine which is no-turbo charged and slightly newer.

author: SilverSolder
author_rank: Super Contributor
timestamp: November 30, 2020, 12:59:51 am
content: Quote from: bdunham7 on November 29, 2020, 10:20:17 pmWhat is actually the best way to measure the wear?

author: bdunham7
author_rank: Super Contributor
timestamp: November 30, 2020, 01:09:26 am
content: Quote from: SilverSolder on November 30, 2020, 12:59:51 amWith and inside micrometer or gauge set and a regular outside micrometer. You can also measure the clearance directly on the top side with a dial gauge and at the bottom using a gauge and geometry as the OP appears to be doing. However, 9 times out of 10 just comparing the lateral movement one way with the other will tell the whole story.

author: SilverSolder
author_rank: Super Contributor
timestamp: November 30, 2020, 05:21:25 am
content: Quote from: bdunham7 on November 30, 2020, 01:09:26 amAh, they don't wear the same in X and Y directions?

author: ssashton
author_rank: Frequent Contributor
timestamp: November 30, 2020, 01:20:05 pm
content: Mine certainly haven't worn equally in both directions, but it seems like there is still some wear in both ways. The worst valve on the intakes has movement (at the head of the valve when extended) of 0.6mm top to bottom but only 0.2mm side to side.I've never seen an inside (aka insize) micrometer that can get in to a 5mm hole. I think aball gaugeis more likely the go to here. You can browse some nice tools here:Cutwel ToolsI got my first quote for installing guides and cutting the seats. £18+tax per valve. Adds up with 16 valves!

author: SilverSolder
author_rank: Super Contributor
timestamp: November 30, 2020, 02:31:13 pm
content: Quote from: ssashton on November 30, 2020, 01:20:05 pmYou know when you open the hood (bonnet!) on a car, it can quickly become a multi-$1,000 rabbit hole!

author: bdunham7
author_rank: Super Contributor
timestamp: November 30, 2020, 03:46:09 pm
content: Quote from: SilverSolder on November 30, 2020, 05:21:25 amWith any valvetrain that puts a side load on the valve, you'll get wear in that direction. Bucket-type lifters avoid this problem because they transfer the side load to the much larger and well lubricated bucket.

author: bdunham7
author_rank: Super Contributor
timestamp: November 30, 2020, 03:58:30 pm
content: Quote from: ssashton on November 30, 2020, 01:20:05 pmInside mic is a generic term. You can use a fixed ball gauge set as a go/no-go, but the two tools for actually measuring are the dial bore gauge and a 'split' ball gauge aka small hole gauge or ball mic.https://www.cylinderheadsupply.com/valve-guide-tools-measuring-tools.htmlIn actual practice, we rarely used either. The valve guides were sized with precision reamers and then automatically checked when cutting the seats because the proper pilot had to fit snugly. So, for example, say we had a head with 5/16" valve stems and a .002" clearance spec. We would measure the valves to make sure they were actually 5/16", then select the 5/16+.002" reamer and size them. Then, you would test that when you got to the next machine by putting in the 5/16+.002" pilot, which was tapered ever so slightly, to make sure it went it most of the way but fit snugly.Just out of curiosity, can you see what the movement on that loose valve is at the top side of the guide? And are your valve seals pliable or are they hard and perhaps cracked?

author: ssashton
author_rank: Frequent Contributor
timestamp: November 30, 2020, 05:09:46 pm
content: Valve seals have a hard body but a soft ring on the top. They seem to fit snug still.How would I check the top side, do I install the valve in closed position and see how much it moves at the top of the stem?I was thinking to save a bit of money maybe I could remove and install the new guides myself then just hand it over for machining. Reading up on it, it seems like heating the head to ~100C can significantly loosen the valve guides (ali expands slightly more than bronze) and then they can be removed and inserted with an appropriate 5mm pin punch / valve guide drift.I was thinking I could place the head in a large bucker of water and use an immersion heater to bring it to near boiling. then tap tap and the guides just fall out, lol?Am I on the right track here or am I likely to just fook the head and I shouldn't worry about saving a few beer tokens?Here is a peak at the head after clean up.

author: bdunham7
author_rank: Super Contributor
timestamp: November 30, 2020, 05:33:16 pm
content: Quote from: ssashton on November 30, 2020, 05:09:46 pmIf the seals still grip the valve stem they likely weren't leaking much. To check the top side, install the valve normally and check it in the 'just-open' position, just enough off the seat to allow it to wiggle freely.I'm not sure you'll save much money doing just the guide pressing and yes, you could make a mess. For example, if you don't get it quite right, the guides can seize and gall the bore in the head on the way out--or in.

author: SilverSolder
author_rank: Super Contributor
timestamp: November 30, 2020, 06:51:44 pm
content: Getting it fixed "the right way" for sub 300 quid is not too bad? I would have expected a lot worse...

author: ssashton
author_rank: Frequent Contributor
timestamp: November 30, 2020, 10:54:55 pm
content: Got a quote for cash from a place quite near me, so I'll be going with that.If this were all I've spent so far it wouldn't feel so bad, but it has taken a lot of time and money to get to this point! Looked a lot like a fuel system problem at the start. Still can't explain why the high pressure fuel went away then came back. I'm not 100% sure this is actually the cause of my issues, but it certainly won't be helping matters.Time to play the waiting game again until the valve guides arrive and I can get the head to the shop.Keep you all updated.

author: ssashton
author_rank: Frequent Contributor
timestamp: March 19, 2021, 10:24:34 pm
content: Hello! I owe you an update!So... I got the head to a machine shop and they replaced all valve guides, re-cut the valve seats, ground the valves in and skimmed the face.I only just got it all re-assembled because I got the head in new year and then got a massive order for my business and was working all hours until this week.Anyway I got it back together today and it runs just like before - misfire on all cylinders!Yeah I did do a compression check and a lead-down test after re-assembly everything was good.I'm done with it now. My Mum is giving me her old but reliable car and I've got more interesting things to take my focus like building a new CNC router

author: ssashton
author_rank: Frequent Contributor
timestamp: March 19, 2021, 10:25:44 pm
content: I should say thank you so much for all the help I got here. I really mean it. The end result didn't work out but that doesn't change the fact I got great support here!

author: SilverSolder
author_rank: Super Contributor
timestamp: March 20, 2021, 08:29:07 pm
content: What a total pain! - but you've got it in such good shape now, apart from the misfire issue - take a break from it and have another go when you've calmed down!We've all been there...

author: ssashton
author_rank: Frequent Contributor
timestamp: March 22, 2021, 06:21:32 pm
content: Nah I'm selling it. I tried to re-flow the ECU and the main CPU took a talk across the PCB. I'm 99% sure it was the ECU at fault and replacement either used or new is not something I want to do anyway. So I'm not too bothered at this point. Selling as good engine duff ECU. Hopefully someone has a track car that needs the engine!