89 GTA 350 TPI, no mods

Here is my problem: The car will start cold ok, if shut off only after a few minutes of running and it will not restart, runs long enough to go into closed loop. If I let it sit for a while it will start up, has a rough idle once it warms up. If I do not shut it off the engine will stay running, does not stall. The engine can run less then 5 minutes and this problem happens. Here is what I know and have checked:
Have spark
Have injector pulse, checked with noid light
No fault codes
New dizzy w/pick up coil and module, no change
new coil, no change
timing is correct
fuel pressure is 40 psi while cranking when it will not start
Compression is good
spark plugs are clean, not carbon fouled
engine vacuum is 20hg at idle
checked ecm and engine related grounds
disconnected the following sensors one at a time: ECT MAF TPS-no change
Can a bad MAF cause a no start?
Can the ECM be bad? Injector pulse timing off?
I am leaning towards an ecm but would like to hear what some of you out there have encountered before I buy one.
Thank you for any suggestions you may have, I am out of ideas and losing my mind with this problem

 

Leaking injectors will cause eng to "flood" after shutdown. If it sits long enough, the gas will evaporate and eng starts normally.

Try holding throttle wide open while cranking. This will put ecm in "clear flood" mode and shut-off the injs while cranking. If this helps, your problem is most likely leaking inj/s.

You can also do a fuel press decay test, but that test only indicates fuel press is leaking off. Doesn't necessarily tell you what componant is leaking. Could be injs, press reg, check-valve in fuel pump, or an external leak (but you would notice that).

To really verify leaking injs, remove plenum and runners, pull-up fuel rails but leave fuel lines connected. Turn ign to run (but not start!) to pressurize fuel system. If injs are leaking you'll be able to see it.

 

my friend had very similar symptoms..replaced a ton of stuff..and it ended up being the stock prom..it had gone bad if you know someone with a prom(chip) for that car give it a try

 

Thanks for the reply, I forgot to mention that I have tried the clear flood mode, no change. I noticed that the noid light has a pulse but it seems dim, the times the car has started with the noid light attached it gets brighter then starts, I have 12v on the fues side of the injectors which makes me think that the ECM is not suppling a good ground. The car seems to run real lean when it does run. With the CTS disconnected the car idles and runs better. Are the ECM grounds under the hood or inside near the ECM?

 

I wish I had a prom or ECM to try, my next step is pick up another ECM but I wanted to see if anyone had any other suggestions. Anyone out there near Middletown NY and want to let me try there ECM as a test? I will throw in a case of beer

 

I really dont think a bad ground will do that much to you. It does sound however to be a bad prom.

 

ttt

 

Try taking out your IAC valve and clean it, as well as the passage way in the bottom of the throttle body.