Idle Speed Control System

Idle Air Control (IAC) System:

PURPOSE
The Idle Air Control System allows for precise control of the engine idle during cold, warm and high load conditions.

Computer And Emission Control Component Locations:

Idle Air Control Valve (IACV) Unit Components:

Idle Air Control Housing Unit (with all idle valves) is on the back side of the intake manifold, driver's side.

OPERATION
Idle speed is controlled by fine adjustment of the amount of air allowed to bypass the throttle valve.

Three different devices, all part of the Idle Control System, are used to control engine idle. These devices are:

1. Idle Air Control Valve-Air Regulator (IACV)-Air Regulator.
- Used to provide additional by-pass air during cold engine operation. Allows cold fast idle. Activated by 12 Volts DC.
2. Idle Air Control Valve-Fast Idle Control Device (IACV-FICD).
- Used to provide a small amount of idle-up when the A/C compressor is turned on. Activated by 12 Volts DC.
3. Idle Air Control Valve-Auxiliary Air Control (IACV-AAC) Valve.
- Used to provide fine control of the engine idle during warm up, and "closed loop" operating conditions. Activated by a duty cycle signal from the Engine Control Module (ECM) at a rate of 100 - 200 Hz.