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.
Removal & Installation
5.4L & 6.8L Engines
- Disconnect the battery ground cable.
- Disconnect the idle air control (IAC) valve electrical connector.
- Disconnect the throttle bypass hose.
- Remove the two bolts and the IAC valve.
Install the IAC valve and tighten the bolts in two stages:
- Stage 1: Tighten to 89 inch. lbs. (10 Nm).
- Stage 2: Tighten an additional 90 degrees.
- Connect the throttle bypass hose.
- Connect the IAC electrical connector.
- Connect the battery ground cable.
- 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.