The Idle Air Control (IAC) valve adjusts the engine idle speed. The valve is located on the side of the throttle body. The valve is controlled by a duty cycle signal from the PCM and allows air to bypass the throttle plate in order to maintain the proper idle speed.
Do not attempt to clean the IAC valve. Carburetor tune-up cleaners or any type of solvent cleaners will damage the internal components of the valve.
The throttle body system meters air to the engine during idle, part throttle, and wide open throttle (WOT) conditions. The throttle body system consists of an idle air control (IAC) valve assembly, an idle air orifice, single or dual bores with butterfly valve throttle plates, and a throttle position (TP) sensor. One other source of idle air flow is the positive crankcase ventilation (PCV) system. The combined idle air flow (from idle air orifice IAC flow and PCV flow) is measured by the MAF sensor on all applications.
During idle, the throttle body assembly provides a set amount of air flow to the engine through the idle air passage and the PCV valve. The IAC valve assembly provides additional air when commanded by the PCM to maintain the proper engine idle speed under varying conditions. The IAC valve assembly mounts directly to the intake manifold assembly in most applications. Idle speed is controlled by the PCM and cannot be adjusted.
Removal & Installation
- Before servicing the vehicle, refer to the Precautions section.
- Disconnect the battery ground cable.
- Disconnect the electrical connector.
- Remove the bolts and the IAC solenoid.
To install, reverse the removal procedure.
- Turn the ignition switch to the OFF position.
- Disconnect the wiring harness from the IAC valve.
- Measure the resistance between the terminals of the valve.
- Due to the diode in the solenoid, place the ohmmeter positive lead on the VPWR terminal and the negative lead on the ISC terminal.
- Resistance should be 6-13 ohms.
If resistance is not within specification, the valve may be faulty.
Before servicing the vehicle, refer to the Precautions section.
WARNINGUse only a high-impedance multimeter, otherwise damage to the PCM and/or sensors can result.
- With the key OFF , disconnect the IAC valve connector.
- Measure the resistance of the IAC valve. Specification is 6-15 ohms.
Replace if out of specification.