Lincoln Aviator, Ford Explorer, Exp Sport, Exp Sport-Trac, Mercury Mountaineer 2000-2005

Idle Air Control Valve



The Idle Air Control (IAC) valve controls the engine idle speed and dashpot functions. The valve is located on the side of the throttle body. This valve allows air, determined by the Powertrain Control Module (PCM) and controlled by a duty cycle signal, to bypass the throttle plate in order to maintain the proper idle speed.

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Fig. Typical Idle Air Control (IAC) valve which is mounted to the throttle body-cutaway view shows air bypass direction


  1. Turn the ignition switch to the OFF position.
  3. Disengage the wiring harness connector from the IAC valve .
  5. Using an ohmmeter, measure the resistance between the terminals of the valve.
  7. Due to the diode in the solenoid, place the ohmmeter positive lead on the VPWR terminal and the negative lead on the ISC terminal.
  9. If the resistance is not 7-13 ohms, replace the IAC valve.

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    Fig. IAC valve wiring harness connections