Mitsubishi Pick-ups and Montero 1983-1995 Repair Guide

Idle Air Control Motor (DC Motor)


This procedure is for 2.4L engines (California-RWD, 1993 and later models)


See Figure 1

The volume of intake air during engine idling is controlled by the opening and closing of the Idle Air Control (IAC) valve for bypassing the throttle valve, located at the air intake port. The DC motor turns clockwise or counter-clockwise according to the change in the direction of current in the motor drive IC inside the ECM. The IAC valve opens and closes depending on which direction the DC motor inside the IAC motor is turning.

While the engine is idling, if the idle speed and IAC valve position (step) change when the air conditioning switch is turned to On and Off, it can be assumed that the idle air control motor and the IAC valve position sensor are operating normally.

If the IAC valve position (step) is outside the standard position, the malfunction is probably one of the following:

Basic idle speed adjustment is wrong.
Some deposit is adhering to the throttle valve.
Air is being drawn into the air intake manifold through a defective gasket seal.
The EGR valve sheet adhesion is defective.
Combustion malfunction inside a cylinder (spark plug, ignition coil, injector or compression pressure is defective.)

Click image to see an enlarged view

Fig. Fig. 1: The location of the idle air control motor, attached to the throttle body-2.4L (California, 1993 and later) engines


See Figure 2

Unplug the IAC motor harness connector and the ECM harness connector. Check for an open or short-circuit to ground, between the IAC motor terminal 5 and the ECM terminal 4, and the IAC motor terminal 6 and the ECM terminal 17. If a short or open-circuit is present, repair the harness between the respective terminals.

Click image to see an enlarged view

Fig. Fig. 2: The harness side connector and terminal numbering-2.4L (California, 1993 RWD and later) engines


For this procedure you will need a sound scope.

This test checks the actuator. Use a sound scope to check the sound of the idle air control servo. Listen to the servo while the ignition switch is turned ON . Shortly after the ignition is turned ON , the sound of the servo should be able to be heard.


The idle air control motor (DC motor) is attached to the throttle body. The air intake hose must be removed, and the throttle body removed from the intake manifold plenum. Label any hoses or cables removed and save all bolts and nuts for re-installation. For further instructions on the removal and installation of the throttle body, refer to Fuel System .