with the IAC removed and the bypass lines plugged i can dial whatever idle i want 450-650 (smooth) with the manual adjustment. i believe this eliminates any possibility of any vacuum leaks or bad ign parts.

when i install the IAC the idle shoots up to 3000 rpm.

i have two IACs both do the same thing

i have verified that the ECU knows that the engine is in idle mode by removing the wire harness and jumpering the lower two connectors in the wire harness plug and the idle speed hiccups when i do this

i have also tried connecting the IAC wires to the UNINSTALLED IAC. it is getting some kind of signal because it clicks and moves

on one of the IACs i have loosened the top section and can adjust the idle down to 750 rpm by rotating the top section, this however is not correct and come winter i don't think i'll see any fast idle

i've read all i can find on this, and i've heard about two unused wires behind the airbox (mine are white/grn and white/rd) which if grounded will either disable the IAC? reset the ECU idle memory? or ground the O2 measure point? out of desperation i have tried grounding both with no results

THIS IS NOT A LINKAGE PROBLEM these tests were done with the linkage rod disconnected, i also do not think that the engine thinks it is cold and is trying to raise the idle or richen the A/F mixture because I've put on about 800 hwy miles in two recent trips, mileage has been good, performance has been great and the plugs look good

the idle speed was PERFECT!! before i cleaned my throttle body

any help would be deeply appreciated

1988 765 ti 265000 km