I have a strange idle problem that has been bugging me. My car has a 305 with a stock carb. Anyways after the car has been warmed up then off for a while when you start the car again the idle goes real low at about 500 rpm and stays there but when i turn on the AC the idle climes to a more stable level. After a while of driving the idle climb to a more stable level at about 1000 rpm what could be causing this?

 

Is there an idle speed solenoid (other than the AC solenoid) on the carb? If so, you may need to "blip" the throttle once after starting to allow the solenoid to extend.