The Idle Air Control Motor (IACM) is found on all vehicles covered by this information except 1988-90 and early 1991 Premier and Monaco models. The IACM is mounted on the throttle body and is controlled by the engine computer (PCM, ECU or SBEC). The engines computer adjusts engine idle speed through the idle air control motor to compensate for engine load or ambient conditions.
The throttle body has an air bypass passage that provides air for the engine at idle (the throttle blade is closed). The idle air control motor pintle protrudes into the air bypass passage and regulates air flow through it.
The engine computer adjusts engine idle speed by moving the idle air control motor pintle in and out of the bypass passage. The adjustments are based on inputs the engine computer receives. The inputs are from the throttle position sensor, engine speed sensor (distributor pick-up coil), coolant temperature sensor, and various switch operations (brake, park/neutral, air conditioning). Deceleration die-out is also prevented by increasing airflow when the throttle is closed quickly after a driving (speed) condition.
Except Early Premier and Monaco
For this test, a Diagnostic Readout Box (DRB or DRBII) or an equivalent diagnostic tool in order to actuate the IACM pintle, while it is removed from the throttle body.
- Allow the engine to warm up to normal operating temperature, then idle at normal engine speed.
- Unplug the IACM connector.
Using a voltmeter, measure each of the four terminals of the connector (wiring harness side) to engine ground (one at a time). 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 .
- Disconnect the PCM/SBEC 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 connector to the PCM/SBEC connector as follows:
- Oxygen sensor connector terminal 1 (gray/red wire)-PCM terminal 39 (gray/red wire).
- Oxygen sensor connector terminal 2 (yellow/black wire)-PCM terminal 60 (yellow/black wire).
- Oxygen sensor connector terminal 3 (brown/white wire)-PCM terminal 40 (brown/white wire).
- Oxygen sensor connector terminal 4 (violet/black wire)-PCM terminal 59 (violet/black wire).
- If the resistance of any of the circuits is below 10.0 ohms, replace the PCM/SBEC. 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 IACM from the beginning.
- Otherwise, continue to the next step.
For the next couple of steps the DRB scan tool or equivalent is required.
- Remove the IACM from the throttle body; leave the harness connected to it.
Plug the scan tool into the data link connector, and actuate the IACM.
- If the IACM pintle extends and retracts, the IACM is fine and should be reinstalled.
- If the IACM does not extend or retract, the IACM is defective and a new one should be installed.
- After any repairs, make sure to retest the system to located numerous trouble spots.
REMOVAL & INSTALLATION
See Figure 1
- Disconnect the negative cable from the battery.
- 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 in. (25.4mm), it must be retracted.
To retract the pintle the DRBII scan tool will be needed. The DRBII scan tool is expensive, therefore, you may need to take the IACM 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.
- Connect the negative cable to the battery.