91 firebird 3.1 shutting down
 

i have replaced the ECM,Distributor,TPS,Knock Sensor,Plugs and, wires as well as a group of other items and when i start it it runs great till it reachs normal running temp it gets rough then dies and wont restart till it is totally cold. 123,000 O/M regular oil changes were always keep up
please help

Re: 91 firebird 3.1 shutting down
 

Did you replace the ICM, ignition control module? When these get hot, they fail and your spark fails. Also, ohm your injectors, check fuel pressure, and check to see whether you have a ruptured diaphragm in your FPR, fuel pressure regulator. Good luck.

Re: 91 firebird 3.1 shutting down
 

yes i did
. heck had a Pontiac dealer went as far as changing the steering column. good fuel pressure it never looses good spark even when it shuts down

Re: 91 firebird 3.1 shutting down
 

Egr?

Re: 91 firebird 3.1 shutting down
 

Wiring harness.

GM had a big recall on engine harnesses for the 3.1 cars. Something about the ignition wiring was run through the harness wrong and would rub through the insulation on the wiring causing problems. My parts worked 100% on the 2.8 harness. Throw the 3.1 harness in and it would shut down randomly when hot but refire after a few second cool down. Remove and swap harnesses again and everything's peachy... Wiring harness fault. Not entirely sure what as I cut up that entire harness and found no damaged wiring anywhere at all but the issue was definitely in the harness. And yes, this was between 2 ECMs and a couple MEMCALs also.

Re: 91 firebird 3.1 shutting down
 

sounds like failing coils in the injectors to me. If they are the stock injectors if they are going to fail it is more common when the injectors are warm/hot. Check the resistance on them.