I have an all original, except K&N filter, flowmaster 1994 Z28, I can fire it up, let it idle 20 minutes to 180 degrees, then it sounds like I have an .750 lift cam and idles like it too......I do not know if I am dealing with vapor lock, The guy I bought it from told me it was doing it. He put a new fuel pump in, that all seems to be alright, once it cools back down, it will fire right back up to do the same thing, I know the optisparks are the biggest plague to mankind, hope that is not it, when I start it up and run it at 2,500 rpm, it will not have this problem at all, only when I idle back down, any help would be appreciated...

 

has the ses light came on? have u checked for trouble codes? could be ignition modual.

 

Or possibly a vacuum leak!

 

With it only doing once your car gets up to temp, I would lean towards it being your coil. However your if it is your coil, it should through a code or bring on your ses light, just like Craby was asking.

 

Just noticed your other thread sounds like that is your problem right there. The IC sends a signal to the pcm to calculate timing, then that signal is sent to the icm, from there it is sent to the coil. according to alldata the voltage should range from .5 up to 4.5 volts(while the engine is cranking). If it reads above or under this your pcm, cuts power to your injectors to stop the ignition system from working.
I attached a diagnostic chart and wiring diagram to help you out. Good luck.

 

Yes the ses light comes on, I do not have an obd 1 code reader, just obd 2, guess i'll have to buy one thanks..

 

Thank you........hopefully I can help with something in return.