car started running poorly,no power, wouldn't rev past 2500 rpm under load or not. 5 speed manual transmission, error codes popped up p0108, p0172,p0300. spark plugs black and sooty.seemed to idle okay after warming up. fuel pressure at 55-60 psi. fuel regulator was replaced(new) since i thought that was high,since found out thats norm. map sensor replaced (new) this resulted in no change. coilpack and spark module exchanged (no change) since i planned on keeping car i purchased a reflashed pcm off ebay, car wouldn't even start with that pcm, returned to original pcm car ran as before. fuel filter was then changed car seems to have worsened as now idle isn't as smooth and rpms unable to exceed 1500.pcm was exchanged per shop manual, battery un hooked etc... almost ready for dealer. any help appreciated,

Sounds like a bad O2 sensor, if your plugs are all covered in soot, its dumping fuel into your engine. What are codes 108 and 172? Isn't 172 an O2 code?. Anyways, let us know.

To LOBO206:
I have the same problem with a 2005 Chevy Classic with a 2.2L ecotec. I don't have the codes with me at this time but I believe that I threw the same codes. I changed the stage 1 O2 sensor with a generic aftermarket and installed new plugs from OReilly auto. Same problems but my check engine light went out. My OBDII code scanner now shows no codes but the car still runs as you stated, no power and the new plugs are black and sooty. I now have mine scheduled for the shop this weekend because I can't think of anything else to check. If you find the problem please post a reply. I will do the same.

i've been thinking even though the plugs are black and sooty, they're dry that makes you think that it;s an abscence of gas even though codes suggest rich. i'm going to pull airbox and spray a little gas in while opening throttle. looking through threads fuel pump issues are common but since pressure is good i hadn't been leaning that way. but perhaps if screen is plugged they're wouldn't be enough flow.

I had the same problem, it turned out to be the catalytic converter, I'd try and pull it and test pipe it, if it clears up there's your problem.



"it's only a cavalier, right?...I mean it's not fast or anything, is it?" -famous last words-

To Lobo206:

Took my 2005 Chevy to the shop. They put it on the diagnostic machine and told me what I already knew. It's not the ignition system. They then went to check the fuel delivery system. Good pressure from the pump to the fuel rail. After that they can't check it, recommend taking it to the dealer.

I have read the replys on this. I would find it hard to believe the cat converter is bad after only 2 years and 30K miles.

I think I will do what you suggest and flow some fuel into the air intake while opening the throttle. If that works I guess I will drain the tank and clean the injectors.

mine only has 40,000 and if i place rag over exhaust exit you can feel quite a bit of backpressure build up also cat doesn't appear to be overheating (no red glow).also no codes even tho you have an o2 sensor for and aft. i didn't have any luck with flowing gas in, might have to use ether as its atomized.i probably won't have time till thurs to try anything new.i was leaning towards pulling injectors also.

Yeah the same thing happened to me and it was my cat.

To Lobo206:

I pulled the first stage O2 sensor off my exhaust manifold and started my car. Without the O2 in place the car runs fine and revs high. The cat convertor is bad and builds up too much back pressure. I am looking for a new one now.

I had the exact same problem. So far the only thing I replaced was the spark plugs. I also thought it would be the ignition system. The only thing I can't figure out though, is that over 4 days, my car went from acting like Lobo206's to almost normal. The only thing is that the car isn't a strong as it used to be though, it feels like it lost maybe 20hp. Think that may be the cat converter or a fuel issue?

To Lobo206:

I have a 2005 Chevy malibu with an ecotec, same problems as yours. The cat converter was my problem. I found out that the cat converter was covered under manufacturers warranty for 8 years or 80 K miles. Took it to a local dealer and they tested the converter and replaced it for FREE! Car runs great again. You might call your local dealer and see if yours is still covered.