Idle Air Control Motor: Operation: Notes
The PCM adjusts engine idle speed through the idle air control solenoid 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 solenoid pintle protrudes into the air bypass passage and regulates air flow through it.
The PCM adjusts engine idle speed by moving the IAC solenoid 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 and power steering).
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 and power steering (also opens the passage slightly before the compressor is engaged so that the engine rpm does not dip down when the compressor engages)