Quote Originally Posted by steveo View Post
these statements apply to any ecm not yours specifically

the iac doesn't have anything directly to do with idle mixture. it uses it to control idle speed instead of moving the throttle plate like a carb or fly by wire engine. the computer meters its fuel to adjust the AFR, it doesn't add airflow to meter its AFR via the IAC. in other words the IAC adds airflow and the computer takes that airflow and calculates the fuel

your idle 'speed' is controlled with most modern ecms by a combination of IAC and timing advance

your idle 'mixture' is controlled by a combination of your VE table (or maf table if maf equipped) and the startup enrichment tables or whatever that takes the coolant temp and/or intake air temp and/or a 'time since start' timer and adds enrichment fuel, this is what replaces the 'choke' in a carb

Yes, but how do i get the iac to "learn" to be in correct position at idle? since for the ECM to adjust tables it needs to have O2 sensor up to temp. Right now my engine surges at idle.
I know i can put it in aldl mode and fully extend it and manually adjust the set screw for the trottle blades, but seems that the whole point of having an IAC is so that this shouldnt be needed?