The Idle Air Control (IAC) motor is mounted on the back of the throttle body. The valve controls the idle speed of the engine by controlling the amount of air flowing through the air control passage. There is a factory pre-set throttle screw located by the valve which is not connected with the valve and should never be tampered with.
The IAC motor moves a pintle shaped plunger in and out of the air control passage. The motor receives an electronic signal from the PCM.
When the valve plunger is moved in, the air control passage flows more air. This raises the idle speed. When the valve plunger is moved out, the air control passage flows less air. This lowers the idle speed.
See Figures 1 and 2
For this test, the Diagnostic Readout Box (DRB III) or an equivalent diagnostic tool is necessary to actuate the IAC pintle.
- Allow the engine to warm up to normal operating temperature, then idle at normal engine speed.
Before testing any electrical component, inspect the wiring and connectors for damage. Also wiggle the connectors to ensure a that they are firmly engaged.
- Unplug the IAC connector.
Using a voltmeter, measure each of the four terminals of the connector (wiring harness side) to engine ground (one at a time). Refer to the accompanying wiring illustration. While probing each terminal to ground, momentarily open and close the throttle.
- If any one, or more, of the terminal circuits registers below 1.0 volt, refer to Step 8.
- If all of the terminal circuits registered above 1.0 volt, proceed to the next step.
- Turn the engine OFF .
- Detach the PCM connector and check to make certain that all of the terminals are clean and tightly installed in the connectors.
- Using an ohmmeter, test the resistance of each of the four circuits from the oxygen sensor and ensure the sensor is working properly. The PCM uses a reference signal from the oxygen sensor to control the IAC motor position. If the oxygen sensor is not working correctly, it will give a false IAC position.
- If the resistance of any of the circuits is below 10.0 ohms, replace the PCM. If any of the circuits register resistance above 10.0 ohms, repair the wire circuit with the high resistance.
Inspect the engine for any vacuum leaks.
- If any leaks are found, repair them and retest the IAC from the beginning.
- Otherwise, continue to the next step.
For the following of steps, the DRB III scan tool or equivalent is required.
- Remove the IAC from the throttle body; leave the harness connected to it.
Plug the scan tool into the data link connector, and actuate the IAC.
- If the IAC pintle extends and retracts, the IAC is OK and should be reinstalled.
- If the IAC does not extend or retract, the IAC is defective and a new one should be installed.
See Figures 3 and 4
- Turn the engine ON for 10 seconds.
- Turn the engine OFF .
- Turn the engine ON for 20 seconds.
- Using the DRB III scan tool or equivalent, actuate the IAC motor.
- With a voltmeter, probe the IAC motors 4 drivers. Refer to the accompanying wiring illustration.
If the voltage is over 5 volts, perform the following test:
- With an ohmmeter, check the resistance of the circuits 1-4 of the IAC driver.
- If the resistance on each driver is below 5.0 ohms on any of the drivers, the drivers circuits are shorted together and must be repaired.
- If the resistance is above 5 ohms, replace the the IAC motor.
REMOVAL & INSTALLATION
See Figures 5, 6, 7, 8, 9, 10, 11 and 12
The Idle Air Control (IAC) motor attaches to the bottom of the throttle body on the 3.3L engine. On the 3.5L engine, the motor is located at the rear of the intake manifold plenum next to the of the left throttle body.
- Remove the PCV air hose on the 3.3L engine.
- Remove the electrical connector from the idle air control motor.
- Remove the idle air control motor mounting screws.
- Remove the idle air control motor from the throttle body. Ensure that the O-ring is removed with the motor.
- New idle air control motors have a new O-ring installed on them. If the pintle measures more than 1 inch (25.4mm), it must be retracted.
To retract the pintle the DRB III scan tool will be needed. The DRB III scan tool is expensive, therefore, you may need to take the IAC motor to a qualified Chrysler dealer to have the pintle retracted.
- Carefully place the idle air control motor into the throttle body.
- Install the mounting bolts and tighten them to 17 inch lbs. (2 Nm).
- Plug the electrical connector back into the idle air control motor.
- Attach the PCV air hose on the 3.3L engine.