OK, if I start my car in the morning and it's ice cold, half the time it doesn't idle fast, it just drops down to about 650-700 and idles rough till it warms up. How do I get fast idle back??

 

Sounds like your IAC sensor could be bad or its stuck and cant move back and forth...

Rick

 

Which car? My '86 IROC (305 TPI) doesn't have a "fast idle" like a carb. engine. My '81Z (350 w/quadrajet) does have a "fast idle" till it warms up. If the problem is with a quadrajet it might be the electric choke (if it has one) isn't working or is out of adjustment. Make sure you have electricity going to the choke when the engine is cold and you turn the ignition switch on. You might have a vacuum leak as well. A vacuum leak (hose, fitting, gasket) seems to affect the engine more when it's cold.

 

if it was a tpi engine, i had that problem. the coolant temp sensor(the one in the intake) was bad on my iroc. i didnt have a fast idle and i found out the that sensor was bad. put in an acdelco unit and now i fast idle in the morning. plus my car was somewhat overheating too and that also was fixed when i replaced the sensor.

 

Mine doesn't overheat, in fact it doesn't get hot at all.. I'll try the new CTS, thanks guys!

 

I hate to bring up this dinosaur thread but I have an 86 trans am 305 tpi with the same exact problem. The car has a new iac, tps, cts, cts pigtail, alternator, battery, and many more. I'll start it up in the morning and the idle will immediately fall to 650-700 and will idle rough, the volt meter will read about 8-9 and when I rev it the needle jumps to 13 and then back down to 8-9, if I restart the car it will fast idle and start normal again.