From: kenny@osf.org (Kenneth Crudup)
Subject: Re: Ford Taurus Computer
Organization: Open Software Foundation
Distribution: usa
Date: Wed, 6 Jan 1993 01:15:04 GMT

In article <1993Jan5.190302.8197@esseye.si.com>
scholten@esseye.si.com (David Scholten) writes:

>I had a very disturbing experience with a dealership's service
>dept. last week.

Well, as much as I hate the Ford EEC-IV computer, (I've been battling it
for a few years now), I'm gonna have to side with the dealer (gasp!) on
this one. Read on:

>I was told that the PT sensor was bad on my car.  It cost $50 to hook up
>to the computer for the diagnostic.  $125 dollars to replace the sensor
>and to clean the plates.  Not knowing what a PT sensor was, all I could do
>is accept their diagnosis.

Don't feel so bad. *I* don't know what a "PT" sensor is. :-) Methinks you
mean you mean "TP" (throttle position) sensor. Unfortunately, however,
putting a "STAR tester" on the car to get the codes is a 5 minute job, but
they charge you $50, just in case the CPU points out something obvious.

It is a good idea to know how to do this. The sensor itself is about $40,
and I dunno labor for doing it on a Taurus, but on my Merkur, the throttle
body has to come off to change the TPS (unless you've got little hands). The
cleaning is actually good for the idle condition. Still, none of that is
as involved as it sounds, and could have been done by any half-brain, (a
good many of whom work in Ford dealerships as "mechanics", unfortunately).

>Well, when picking up the car and getting the bad part, I realized that
>a PT sensor was nothing than a potentiometer.

Yup, it's a pot that tells the computer how far you've "put the hammer
down".

>I took the part home and have sinced ohmed it out to discover that nothing
>was wrong with the original part.  I really feel like I got took!

Not necessarily. Have you had an old table radio that had a "noisy" volume
control? All that was was a pot with some continuity breaks and maybe some
dust, and this was in the safe environment of the home. Now, imagine that
since 1987, that there's some pot under the hood of your car, sealed up,
but still subject to all those heat/cold/wet cycles and gets moved every
time you move your foot. Get the idea? Even though an ohmmeter will give
you good readings at each extreme, and readings in the middle, small noise
variations will show up to the computer, and the computer will set a code.
It *has* to know where the throttle is, and repeatability and a solid, un-
varying signal is a big requirement.

>The real irony to the story is that the car runs worse than it did before.
>When I took it back, they claimed that it didn't exhibit any of the symptoms
>I was complaining about.... so nothing touched.

If they were halfway competent, they cleared your error codes by disconnecting
the battery. However, this also makes the computer re-learn the condition of
the vehicle (and the new sensor as a nice side effect), so for the first few
starts, it won't be as it was when it's settled down. If it persists after
a few days, COMPLAIN! Despite what I've said so far, they still could have
been wrong about the sensor (Yeah, buddy, that's 'cuz your TPS is bad- we
see that all the time), or they screwed something else up (it happnens to me
anytime I let some grease monkey work on my car- that's why I do most of
it myself). Did they adjust your idle as well after they had the new TPS in?
If that's not on the work order DEMAND that they do it.

Hope this helps,
	-Kenny

-- 
Kenny Crudup, Contractor, OSF DCE QA
OSF, 11 Cambridge Center, Cambridge, MA 02142	+1 617 621 7306
kenny@osf.osf.org			OSF has nothing to do with this post.
	  Religion: The longest-running gag ever played on Mankind.
Xref: sparky rec.autos.tech:17681 rec.autos:31437