I set my base timing to 8* (spout disconnected) and my base idle to 425/450. Plugged the IAC back in and the idle seems high. My question is this...can I back out the idle screw to manually lower the idle without affecting anything if I make sure the TPS voltage is .54 when I'm done?

Thanks in advance...

 

If you base idle is 425/450 and the TPI Voltage is .54 then you are OK. Once you plug in the IAC, the throttle stop screw setting is irrelevant as long as it is lower than the ECM controlled Idle speed. IAC and ECM programming controls the actual engine idle speed when running. Turning the Throttle stop screw with the IAC plugged in and operating is useless, except that it changed the TPS Voltage and screws with the ECM. For Example, My TPI equipped 310 El Camino has a base idle set at 475 and the ECM controlled Idle speed of 650. TPS voltage is .54 closed with the throttle stop set to yield 475 rpm without IAC.

 

That is kind of what I thought. It is just that I set the base at 425/450 and after plugging the IAC back in the idle seems high. Could the setting be set high in the PROM? Should I go through the process again after the motor breaks in?