Below is a thread I posted on 9/11/07, but I didn't get any replies. I'm really desperate here. Since this post I've replaced the distributor cap and rotor, CTS, and checked the EGR (seems to hold a vacum). Also I tried putting the car in limp home mode and problem is still there. It seems like the car is running way too rich, but I am at a loss as to where to go from here. Any reccomendations are appreciated!!!



I have an '89 trans am (305, TPI, 5-speed, 80k miles) All of a sudden after filling the gas tank my check engine light came on. Car ran fine for 15 miles or so then began to run very rough with loss of power. After putting it away for a few days I went to start it up and it ran fine so I reset the computer before getting any of the codes. Took it for a drive later that day and it started acting up again only after it got to operating temp. I thought it was just bad gas so I put about 300 miles or so on it but fresh gas didn't help. The check engine light has not come back on since I reset it. I replaced the 02 sensor thinking once it was running on a closed loop it started acting up. Runs fine when cold but sounds very "flat" when it warms up. Doesn't stall and no problems starting. Sorry for the book, but I'm at a loss here. I don't trust taking it anywhere around here so any help would be appreciated!!

 

Nothing???

 

Was it on empty when you filled it up? When have you changed the fuel filter?

 

it was 1/2 full when I filled up and the fuel filter was replaced a 2K miles ago.

Anyway it can be the fuel pressure regulator? I'm just trying to narrow it down between sensor/fuel or ignition.

 

Probably not the fpr because that would act up whether it was hot or cold. It sounds like you're on the right track with regard to the problem being related to closed loop/feedback mode. Could be the engine temp sensor, MAF, etc. You didn't mention what code(s) was popping up. That would help narrow down what's going on.

 

Does it keep fuel pressure when it acts up?

 

Unfortunately the engine light hasn't come on to get codes. I haven't checked fuel pressure either. Does anyone know of a good way to check if the MAF is bad? I did take the screens out, but the thin wire seems to be intact. Also would using a laptop with diagnostics software be a benefit for this type of problem? Thanks a lot for your help guys!!

 

It doesn't matter if the fuel filter was changed 2k miles ago, it could be clogged. Start with the basics, check your fuel pressure on the rail, if it's really low, check it behind the filter, if it's ok there; clogged filter.

As far as the mass air; simply unplug it when your car acts up, it's not going to idle very well, but if it's bad it should run a little better.

Also check your exhaust: EGR, cat ect... the EGR could be sticking or your cat could be plugged.

You need to figure out what your losing, fuel/spark/air ect... before you try complicating things with computer diagnostics.