First forum post, just picked up a 92 and love the car. I am having an idle issue when the a/c is running, the idle drops to about 300, and sometimes stalls. The car makes no attempt to adjust the idle when the a/c kicks on. The car runs and idles fine all other times. I have read several forum posts and checked in the service manual. I did the pin TEN to GND test and it idles right at 750-800. I put a meter on the valve connections and it reads 12.5-13. I did the click test (unplugging the valve with the engine idling) and it works as well. Only thing I can figure at this point would be the computer is not getting a signal that the a/c is running? Just wanted to see if anyone had any insight before I start into the wiring.

 

Is the IAC valve sticking? They get carbon clogged and bind up sometimes.

Did you check the base timing to make sure it is 10 degrees? Actually 15 degrees is better than the stock 10 for peppiness.

I actually idle mine at 1050 rpm on an aftermarket computer to help keep it from stalling when it dips.