Alright, this isn't my Camaro, but it's a GM. I have a '99 Grand Prix GT (3.8L) that about a week ago started giving me problems. I drove it to the gym after work and when I came out it would not start. I had it towed home and since then have found out that it starts fine cold, and will run fine until I park it. Then unless I wait many hours 'till it has competely cooled down, it will not start, or if I can get it started it is running extremely rich.

I have AutoTap and it is not throwing any codes. Following are things I have checke or replaced.

Replaced plugs & wires, check spark from all Coil packs.
Replaced front O2 Sensor.
Cleaned MAF sensor.
Checked IAT & ECT sensors though AutoTap and they seem fine.
Checked MAP sensor with meter & hand vacuum pump.
Vacuum @ idle is about 20 in hg.
Fuel pressure 44 psi KOEO, drops to 40 at idle (in line with Haynes manual).
Fuel pressure will hold for over an hour when the key is shut off.

This is getting frustrating, anyone have any suggestions?

thanks

 

I would have said an injector was sticking but you saw the pressure after shut down was ok. That is a weird problem. That would lead me to believe you're loosing spark after it heat soaks for while. Either that or compression but that is highly unlikely. Try heating up a few pieces of the ignition system one at a time while the car is dead cold with a blow dryer. Make them just slightly too hot to the touch and try to start it after each one.

Also, OBDII have 2 reporting modes, standard and generic OBDII. Use a Snap-on scanner (the only one I know of that has that feature) to scan for codes in generic OBDII. We were told by Snap-on scanner guru to start in generic OBDII first and then go to standard mode. May help.