I have a lady friend that I am desperately trying to fix her "misfire" problem. She has to drive this car daily (commutes to work) and it's only running on 3 cylinders! They car has 102K on it and so I started with replacing the plugs. Didn't fix it. I have been reading on here and other blog sites that it may be the Ignition Control Module, coil pack, or possibly an injector? I really don't want to throw parts at it, but she can't afford to take it in and have it diagnosed. I also had her try some Lucas Fuel Treatment, but that only made a slight difference, but it still misses. Oh, and the CEL is on constant until you accelerate, then it flashes. I truly appreciate any help. God Bless!

 

Not knowing what engine is in it do a compression check first to make sure its not a valve problem.

 

If your getting spark, since you put the lucas in, and made it better, probably is getting what it needs. Take an extension with it running, and gently tap on the injector using a hammer. The cel is telling you something, I suspect misfire, do you know what cylinder it is?

 

It's the 2.2 L Ecotec. Cylinder #4 Misfire.