Idle Speed Adjustments

BASE RPM ADJUSTMENT
A base RPM adjustment is not normally required and should not be performed on 1988 (VIN W ) vehicles unless the base idle stop screw had inadvertently been misadjusted during servicing.

NOTE: If the ECM is without battery power for any reason, then the IAC VALVE position information for a stable satisfactory engine idle is lost and is replaced with a default value.

IDLE LEARN PROCEDURE
Any time the battery is disconnected, the programmed position of the Idle Air Control (IAC) valve pintle is lost, and replaced with a "default" value. To return the IAC valve pintle to the correct position, perform the following procedure:

1. Install the Tech 1 "SCAN" tool.
2. Ignition "ON" engine "OFF".
3. Select the "IAC SYSTEM", then "IDLE LEARN" in the "MISC. TEST" mode.
4. Proceed with the idle learn as directed by the Tech 1 "SCAN" tool.