Here are a few ways to tell if you have a clogged fuel injector:nnNot firing on all cylinders: When your cylinders aren’t firing up properly, you cannot listen them. Whether you have a 4, 6 or 8 cylinder car, you will still be able to hear them. If you’ve recently started your car and can see gasoline on your spark plugs then it means you have a clogged fuel injectornForcing Your Engine: If you feel like you have to force your engine to start every time you think of going for a ride outside then it is a strong indicator of a clogged fuel injector. Your injectors release a mist of gasoline and when your cylinder are not firing up properly, it results in unbalanced results. Ideally, you should be able to hop in the driving seat, turn on the key and start your car smoothlynLower Fuel Economy: Cars with a digital meter display current MPG. Closely monitor it, at least once per ride. If you usually travel to same place, like your work place, to and fro, including on and off traffic and also on and off highway, and notice a significant decrease in your MPG, such as 3-4 less MPG than normal, it is usually an indicator of lower fuel economy. Although a clogged fuel injector cleaner might be a cause but there are other reasons as well like spark plug misfiring, bar air filters, incorrect tire pressure and much more