Idle Speed/Throttle Actuator - Electronic: Testing and Inspection

NOTE: This test is performed with the use of an exerciser tool (Part # 7558).

CAUTION: Use the following safety precautions before starting this test.

^ Set the parking brake and block the rear wheels.
^ Make sure all testing equipment and cables are routed clear of the cooling fan, pulleys, drive belts, and exhaust components.
^ Make sure there is proper ventilation for the exhaust gases if the tests are to be performed in an enclosed area.
^ Always return the engine to idle before disconnecting the exerciser tool.

Idle Air Control (IAC) Motor Testing (Typical Installation):

1. With the ignition switch OFF, disconnect the Idle Air Control (IAC) motor electrical connector at the throttle body.
2. Plug the exerciser connector into the IAC motor.
3. Connect the red lead of the exerciser tool to the positive terminal of the battery, and the black lead to the negative terminal. The red LED light on the exerciser tool will illuminate when the tool has been properly connected.
4. Start the engine.
5. There is a switch on the exerciser tool that can be switched from HIGH to LOW or vice versa, this is used to send pulses to the IAC motor. There is a light next to the HIGH-LOW switch that will flash when pulses are being sent to the IAC motor.
6. Move the switch to the HIGH position and the idle speed should increase. Move the switch to the LOW position and the idle speed should decrease.

^ If the idle speed changes according to the position of the switch, the IAC motor is functioning properly. Disconnect the exerciser tool and reconnect the IAC motor electrical connector to the IAC motor.
^ If the idle speed does not change when the switch position is changed, leave the exerciser connected, turn the ignition switch OFF, and proceed to step 7.

7. Remove the idle speed stepper motor from the throttle body.

CAUTION: When checking the operation of the idle speed stepper motor, removed from the throttle body, be careful that you do not extend the pintle more than .250 in. If the pintle is extended further than .250 in, it may separate from the idle speed stepper motor. If the pintle separates from the motor, it is necessary that the whole part be replaced.

IAC Motor:

8. With the ignition switch OFF, switch the exerciser tool between HIGH and LOW, and observe the movement of the pintle.

^ If the idle speed stepper motor pintle does not move, replace and retest as described in step 6.
^ If the pintle operates properly, check the idle speed stepper motor bore in the throttle body for corrosion or blockage and clean as necessary. Reinstall the stepper motor and retest. If no blockage is found, see manufacturers instructions for exerciser tool.