The Idle Air Control (IAC) motor is mounted to the throttle body and is operated by the engine controller. The throttle body has an air control passage that provides air for the engine at idle(when the throttle plate is closed). The IAC motor pintle protrudes into the air control passage and regulates air flow through it. Based on various sensor inputs, the engine controller adjusts engine speed by moving the pintle in and out of the air control passage. The IAC motor is positioned when the ignition is turned to the ON position.
The IAC motor is used on 1992 MFI, as well as all 1993 and later vehicles. For 1989-92 TBI vehicles, refer to the Idle Speed Control (ISC) Actuator procedure, later in this section.
See Figures 1, 2, 3 and 4
To perform a complete test of the IAC motor, you will need the DRB-II scan tool, or equivalent. This test is a test of the IAC motor only. You will need access to the special factory IAC motor exerciser tool No. 7558 or equivalent.
Take the following precautions before beginning:
- Remove the engine cover.
- With the engine OFF , unplug the IAC motor wire connector.
- Plug the exerciser tool No. 7558 harness connector onto the IAC motor.
- Connect the red clip of the exerciser tool to the positive battery terminal, and the black to the negative battery terminal. The red lamp will illuminate when the tool is properly connected.
- Start the engine. When the switch is in the high or low position, the lamp on the exerciser tool will flash. This indicates that the voltage pulses are being sent to the IAC stepper motor.
Move the switch to the HIGH position. The engine speed should increase. Move the switch to the LOW position. The engine speed should decrease.
- If the engine speed changed predictably while using the exerciser tool, the IAC motor is working correctly. Disconnect the exerciser tool and install the IAC motor wiring connector on IAC motor.
- If the engine speed does not change, turn the ignition OFF and proceed to Step 6.