We have an 89 GTA 350 tpi. 6 yrs. ago it broke down and wouldn't run. Hard to start, lopes, backfires, etc. Over these years my husband will go out and work on it thinking we have the problem fixed only to find out the next day it's not.

We have changed the computer, fuel injectors, intake gasket, MAF, coolant temp sensor, ignition control module, distributor, iac, plugs (twice!) and just about everything we could think of. We have done numerous tests over and over again on the fuel system and everything is reading as it should.

The only thing we have not changed is the EGR Valve. Would it cause these symptoms?

Yesterday after changing sensors again it ran perfect and as usual the next day it was back to acting up.

Doesn't want to start. Will start for a second and die. After the 4th try it starts. Revs up high then about dies. Lopes like this several times before it finally dies. Also when you go to give it gas it has a hesitation to it. I just don't understand how we can get it running pefect but after sitting overnight it goes back to the way it was. Could the EGR valve cause this? Any suggestions would be very helpful. We've never owned a Trans Am that has given us this much trouble!

 

Whats the fuel pressure at?

Have you checked the TPS?

Do you have any way to read the ALDL data? Any SES codes?

 

Changed the TPS. There are no codes and the only one that ever showed up was 22 and that was about 6yrs ago when it started acting up. Fuel pressure is 43. We hooked a scanner up to it a long time ago but I don't remember the readings but nothing seemed to be really off.

 

Have you changed the idle air control valve? I didn't see it listed. If you installed a new one but did not reset it after doing so, it can do this. I have a video on youtube that illustrates it.

 

Yep. Changed that too!

 

There are still a few things it could be, but start simple and work from there.
I would put a fuel pressure gauge on it and monitor it closely, also check for pressure/vacuum in the fuel tank.
I'd also go over the wiring closely - fusable links at starter, and the grounds on the back of the heads to ensure a good and tight connection.
I would also eliminate possible vacuum sources as causes, - that means pulling and plugging off ALL vacuum lines, to include the EGR, brake booster, heater valve, cruise control, CCP, etc...

Pull the valve covers, inspect all of the springs and watch valve operation.

There's a few ideas to continue the troubleshooting.

FYI, you can unplug the IAC when it's in the CLOSED position, to eliminate that as the cause of your problem.