Idle Up Control Valve: Description and Operation

Typical Idle Air Control (IAC) Valve:

Purpose
The Idle Air Control (IAC) valve assembly controls engine idle speed and provides a dashpot function.

Operation
The IAC valve assembly meters inlet air around the throttle plate through a bypass within the IAC valve assembly and throttle body. The PCM determines the desired idle speed or air bypass and signals the IAC valve assembly through a specified duty cycle. The IAC solenoid responds by positioning the IAC valve to control the amount of bypassed air. The PCM monitors engine rpm and increases or decreases the IAC duty cycle in order to achieve the desired rpm.
The IAC valve assembly Is NOT ADJUSTABLE and CANNOT BE CLEANED.

Features
The PCM uses the IAC Valve Assembly to control:


^ No touch start


^ Cold engine fast idle for rapid warm-up


^ Idle (corrects for engine load)


^ Stumble or stalling on deceleration (provides a dashpot function)


^ Over temperature idle boost.