Hi everyone, i would be so glad if you could help me out with my problem. Im trying for two weeks now to set the IAC on my 89 305 TBI. I've read all the suggestions, experiences, manuals,. I've done everything. How i did it was: paper clip on Aldl on the A and B. Key on posotion, engine not started, waited 30 sec than unpluged the connector, started the engine, udjusted the rpm with the min air screw to 550 (its not going lower), checked for the TPS voltage and set to 0.54, switched of the key, connected connector back to IAC. My timing is on 0 degrees.
Paper clip removed, engine started, idleing fine on 750-850. The moment i switch of the engine and start again it goes back to 2000rpm idle. Doesnt matter how many times I tried, with unplugging battery or other tips I tried I've read its always the same. First start perfect, second back to 2000rpm with warm engine on neutral. Please if anyone has any idea what else to do...

 

Connect a scan tool, look at commanded idle speed vs. actual idle speed.

Then look at the rest of the sensors and actuators--anything out-of-place or out-of-range?

I'd also be looking for vacuum leaks.

 

I just ordered the scan tool, not really sure what to look for there bit will try. Do you think a leak would be possible if the car is running with first start after adjustment properly, even if I let it run for longer time? If there would be a leak it would affect the idle immediately or not? It looks like the ECM doesn't remeber the new IAC position

 

It sounds like a bad ecm, have you tried wrapping on the case of the ecm while it’s running to see if it stalls or the idle drops ?