Idle Speed/Throttle Actuator - Electronic: Description and Operation

Hitachi Idle Air Control (IAC) Valve And Solenoid:

Nippondenso Idle Air Control (IAC) Valve Assembly:

PURPOSE
The Idle Air Control (IAC) valve is used to control engine idle speed and dashpot functions.

OPERATION
The IAC allows air to bypass the throttle plates for curb idle and fast idle speed control. The amount of air allowed to bypass is determined by the Powertrain Control Module (PCM) and controlled by a duty cycle signal.
The IAC controls:
- Cold engine fast idle
- No touch start
- Dashpot
- Over temperature idle boost
- Engine idle load correction

There are three types of IAC valves, refer to images for identification.

CONSTRUCTION
The IAC valve is a duty controlled solenoid sealed in a metal housing.