Last April I bought my first F-body. Now, it's running like crap. When you stomp on the gas, it bogs, and it bogs bad. Like it won't gain enough RPM to accelerate. No backfiring, no popping, or spitting, just Stumble, stumble, bog... It often idles rough, sometimes it dies. Sometimes it bogs so bad, it dies on the road, and starts hard. This has been getting progressivly worse for the last few weeks. Now, the car's not even drivable.

But... It only does it when the car's good and warmed up. It runs great when it's cold. You can drive it 15-20 miles before it will act up. it'll start with a slight bog, then more bogging, then die, and won't restart. If we let it sit 30 minutes, It'll start again, but run rough. When it dies, and doesn't start, the injectors are not pulsing, and it is not spraying gas.

After a week and a half of searching here, and trying different things, it's still not any better. Here's what we've tried so far:
Cleaned the IAC
Cleaned the EGR and EGR passages
Removed and cleaned the TB, replaced base gasket
Replaced the injector/FPR assembly with one from another TB
Checked the TPS for proper operation, both when hot and cold
Checked fuel pressure, it hovers around 11-12 PSI
Replaced the fuel filter
Cap, rotor, plugs and wires
Replaced the ignition module in the ditsributer

I'm at my whits end with this car. All that and still no progress. To make matters worse, the SES light doesn't work, so I can't pull codes. I have a post about that in another section. I'm almost to the point where I want to just take the car to a dealer, but I know it's probably just a simple little problem. Any help yu can provise would be greatly appreciated. Thank you for your advise.

-Erik

 

I have 2 suggestions. Check all of your vacuum lines. Trace all of them and make sure they are all hooked up and aren't cracked, split, leaking, etc. My other suggestion is to try replacing the oxygen sensor (AKA O2 sensor). Your car sounds like it runs fine in open loop, but once it warms up and hits closed loop, it runs bad, which leads me to suspect that the O2 sensor is fouled or has gone bad.

 

I agree with Benm. it sound slike you have a bad 02. When they go bad they don't always throw a check engine light.

 

Yup agree also. Although I had similar problems and it ended up being my cat. It was so cloged that it was basically sand.

 

Sounds like a bad coil or a weak fuel pump. What is your fuel pressure under load?

 

O2 or something igntion related that fails as soon as it itself (not neccesary the engine's tempature) get's too hot and becomes useless.

 

I tried a spare coil I had from another motor. That didn't help. I tried another O2 sensor, that didn't help either. I remembered that I checked the fuel pressure when it was running good, but never when it wouldn't start. So, on a whim, I hooked my fuel pressure guage back up, low and behold, no pressure. I let the car sit 30 minutes or so, and it started right up with good pressure. Then over the course of the next 15 minutes, I watched the fuel pressure go from 12 to 10 to 8 then to 5, then 0. Damn. Even as a noobie, I know what that means, and the job I have ahead of me.....

 

I would replace it with a Walbro pump or a stock TPI replacement pump. That is unless you don't have any future plans for big power. It isn't too bad of a job. People make it out to be impossible. As long as you get he rear end of the car pretty high and can remove the rear section of your exahust, the rest just boils down to lowering the rear and removing the tank. With my car in the air I was able to change my fuel pump just under 2 hours. I can now do it much faster.