Hi,
I have a bone stock 89 Trans am 305 TPI 86k miles which runs beautiful, that is off idle. The engine pulls like crazy and is smooth as glass anything past idle. At idle though the motor stumbles almost like its missing. I replaced the IAC and cleaned the port, no change. I checked the fuel pressure and I believe its bit high, 36 when idling and 43 with key on and not started. Those number are about 4lbs over the manual specs. Could that be causing the bad idle? If so am I looking at a bad pressure regulator? Fuel pump? maybe the stock injectors?
Any insight would be greatly appreciated.
Thanks

 

cant help much, but would love to hear what it is when you find out, mine is having similar issues, however it is always not jus at idle

 

does it run rich also? my car has a very slight idle that is also off.. you can clearly hear it.. but this car is also running insanely rich so I think that has some possibility of a slight rough idle.. otherwise like you, the car has zero issues when you step on it..

 

I may be off target, but have you checked the resistance of your injectors?

 

yeah that were all good.. I also removed the connectors to each injector and the car did what it was supposed to while idling.. drop down a little bit.. however the car still had the same symptoms of a slight rough idle/misfire.. I'm going to check the memcal.. it's suggested there is a possibility that they never changed it from the 305 that was in the car originally.. so far I'm pretty happy I haven't thrown money at it yet.. but it might not be too far off.. lol