Several methods to reset Idle Air Control

[TedC]

OK, will the right IAC reset procedure please stand up!!! The 1989 GM service manual says "depress accelerator pedal slightly, run engine for 5 seconds, and turn ignition off for ten seconds". The Helms 84-96 manual says "no adjustment of the IAC is necessary. The ECM will reset idle speed the first time the vehicle is driven at 35 mph". A post on this forum says "jumper ALDA A & B, turn on ignition, don't start engine. wait 30 seconds, with ignition on disconnect IAC, then turn off the ignition and disconnnect ALDA A&B jumper". Maybe all these procedures are correct, and it doesn't matter.

 

[c4c5specialist]

HI there,
Actually, it does matter.
The GM service manual, if you look under "minimum air rate" should give you what you need to correctly reset the IAC for correct idle response without hunting.
ALWAYS refer to the GM service manuals before ANYTHING ELSE.
There are no service manual updates to setting minimum idle air rates.
Allthebest, c4c5

 

[TedC]

c4c5specialist, The only reference I can find in the 89 GM service manual on minimal idle air rate is in the fuel metering system section; "set at the factory with a stop screw. This setting allows enough air to flow by the throttle valve to cause the IAC valvle pintle to be positioned a calibrated number of steps from the seat during controlled idle". The next paragraph outlines the steps to reset the IAC which I provided before. There is a dedicated section on the IAC valve check and it states "each time engine is started and then ignition turned off the ECM will reset the IAC valve. The fully seated valve is the ECM reference zero".