Idle Air Control Valve Assembly

WARNING: This page does not describe the selected car, but rather 31 other vehicles, including the 2003 Mercury Sable, 2003 Mercury Mountaineer, 2003 Mercury Marauder, 2003 Mercury Grand Marquis, and 2003 Lincoln Town Car. However, it is still accessible from the selected car via links, so may be relevant.

Idle Air Control (IAC) valve assembly is used to control idle speed and provide a dashpot function. IAC valve assembly meters inlet air around the throttle plate through a by-pass within the IAC valve assembly and throttle body. See Fig 1-Fig 3 .

The Powertrain Control Module (PCM) determines desired idle speed or air by-pass and signals the IAC valve assembly through specified duty cycle. The IAC solenoid is built into IAC valve assembly. IAC solenoid responds by positioning the IAC valve to control amount of air by-passed. PCM monitors engine speed and adjusts IAC duty cycle to achieve desired RPM. IAC valve assembly is not adjustable and cannot be cleaned.

On applications with air assisted injectors, IAC valve supplies a small jet of air into path of fuel injectors, creating an increase in fuel atomization at low speed and light load conditions. See Fig 2.

Fig 1: Cross-Sectional View Of Idle Air Control Valve Assembly With Air Vent/Filter (Hitachi)

Courtesy of FORD MOTOR CO.

Fig 2: Cross-Sectional View Of Idle Air Control Valve Assembly With Air Assist Injectors (Hitachi)

Courtesy of FORD MOTOR CO.

Fig 3: Cross-Sectional View Of Idle Air Control Valve Assembly Components (Nippondenso)

Courtesy of FORD MOTOR CO.