Silhouette V6-191 3.1L VIN D TBI (1995)
Idle Speed/Throttle Actuator - Electronic: Description and Operation
Idle Air Control (IAC) System
Idle Air Control Valve
IAC System
Engine idle speed is controlled by the Powertrain Control Module (PCM) through the Idle Air Control (IAC) valve mounted on the throttle body. The
PCM sends voltage pulses to the IAC motor windings, causing the IAC pintle to extend or retract a given distance (number of steps or counts) for each
pulse. The pintle movement controls the air flow bypassing the throttle valves, which in turn, controls engine idle speed.
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Engine idle speed is a function of total air flow into the engine based on IAC valve pintle position + crankcase ventilation valve flow + throttle
valve opening + calibrated vacuum loss through accessories.
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Controlled idle speed is programmed into the PCM, which determines the correct IAC valve pintle position to maintain the desired idle speed for
