Idle Up Control Valve: Service and Repair

NOTE: The minimum idle air rate is set at the factory with a stop screw, which is covered with a tamper plug. This setting allows enough air flow by the throttle valves to cause the IAC valve pintle to be positioned a calibrated number of steps (counts), from the seat, during "controlled" idle operation. If the IAC valve is disconnected and reconnected with the engine running, the idle speed may be wrong. Do NOT attempt to remove the tamper plug and/or readjust the stop screw. Misadjustment may result in poor idle quality and/or severe driveability problems. if the IAC valve is suspected as being the cause of improper idle speed, a functional check of the IAC Valve is recommended. To relearn the IAC valve for idle, perform the following:


1. Disconnect the negative battery cable for at least 60 seconds then reconnect negative battery cable.
2. Start vehicle and allow to idle until "Closed Loop" operation is established.
3. Drive vehicle above 42mph for at least 2 to 3 miles.
4. Allow vehicle to idle to ensure a desired idle is maintained.