300M, Concorde, Intrepid, LHS, 1998-2004

Idle Air Control Motor


Description & Operation

The idle air control motor (IAC) is attached to the throttle body. It is an electric stepper motor. The PCM adjusts engine idle speed through the idle air control motor to compensate for engine load, coolant temperature or barometric pressure changes. The throttle body has an air bypass passage that provides air for the engine during closed throttle idle. The idle air control motor pintle protrudes into the air bypass passage and regulates airflow through it.

The PCM adjusts engine idle speed by moving the IAC motor pintle in and out of the bypass passage. The adjustments are based on inputs the PCM receives. The inputs are from the throttle position sensor, crankshaft position sensor, coolant temperature sensor, MAP sensor, vehicle speed sensor and various switch operations (brake, park/neutral, air conditioning). When engine rpm is above idle speed, the IAC is used for the following functions:

Off-idle dashpot
Deceleration air flow control
A/C compressor load control (also opens the passage slightly before the compressor is engaged so that the engine rpm does not dip down when the compressor engages)

Target Idle

Target idle is determined by the following inputs:

Gear position ECT Sensor
Battery voltage
Ambient/Battery Temperature Sensor
MAP Sensor

Removal & Installation

  1. Disconnect the negative battery cable.
  3. Disconnect the IAC electrical connector.
  5. Remove the IAC mounting screws.
  7. Remove the IAC.

    Click image to see an enlarged view



To install:

  1. Install the IAC to the throttle body.
  3. Tighten mounting screws to 5.1 Nm (45 inch lbs.) torque.
  5. Attach electrical connector to the IAC.
  7. Connect the negative battery cable.