1990 Firebird Won't Start After Hot Soak

[Thadius856]

A BIG thanks in advance for reading this and (hopefully) responding.

My 1990 Firebird 3.1L EFI very recently started having some issues starting after a hot soak. I can't attribute any event to the change, like running over an animal. They seem to have randomly started.

If parked and left for more than a few hours, the engine will start easily and seems that it will run for as far as I like, so long as I don't turn it off. Once off, the vehicle refuses to start until my temperature gauge reads somewhere in the 100-110F range.

When it's having these issues, the starter clicks and turns over normally, but idle never occurs. Cranking for two seconds or thirty makes no difference, nor does anything I've tried with the fuel petal. Battery charge reads normally (12.5 or so), as does temp. "Check Engine" light is observed until key is turned, but has been with every start since I bought the vehicle 7 years ago and have been assured by several mechanics that it's a normal condition with the key in Acc.

Twice I've been able to get the engine to start while hot, but it sputters and runs horribly until revved in park past 3k RPM. Shifting into gear causes it to sputter again, regardless of how fast the vehicle is moving. I was able to make it home once sputtering like that (emergency), though it sounded like driving a VW bus. Power was very low and I was unable to hold my speed on hills as small as a 3% grade.

The last time it did this, I removed the air intake and cranked the engine over. I noticed no changes, but did observe a wispy grey smoke or steam being emitted.

Any help with further diagnosis would be greatly appreciated!

[91 bird]

i had a problem like that on my 3.1 once. it turned out that the wire harness for the injectors had a short in it. it would shut down one or two injectors while running. the heat may be causing wires to expand causing this short. when cool, they contract causing the short to disapear. i had to install new wires around the harness. the problem has not come back. its been five years now. hope this helps.