Neon, 2000 - 2005

Description & Operation (7 of 19)


The Idle Air Control (IAC) motor is mounted on the throttle body. The PCM operates the idle air control 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 IAC 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 TP sensor, CKP sensor, ECT sensor, MAP sensor, VSS, 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)

Click image to see an enlarged view



Target Idle

Target idle is determined by the following inputs:

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

When servicing throttle body components, always reassemble components with new O-rings and seals where applicable.

NEVER use lubricants on O-rings or seals, damage may result. If assembly of component is difficult, use water to aid assembly. Use care when removing hoses to prevent damage to hose or hose nipple.