Lumina APV V6-3800 3.8L (1994)
Idle Speed/Throttle Actuator - Electronic: Description and Operation
Idle Air Control Valve Assembly (IAC)
PURPOSE
The IAC valve is used to control the engine idle speed and prevent stalling due to changes in engine load.
LOCATION AND OPERATION
The IAC valve, mounted in the throttle body, controls the amount of air bypassed around the throttle plate. If more air is bypassed, idle speed will
increase, and if less air is bypassed, the idle speed will decrease. The IAC valve accomplishes this by moving a conical shaped pintle in to decrease
bypassed air and out to increase bypassed air. This can be seen as counts as displayed on a "Scan" tool. Inward Movement of the pintle = Decreased
RPM = Lower Counts. Outward Movement of the pintle = Increased RPM = Higher Counts. The PCM uses sensor and switch inputs to control the
position of the IAC pintle. If the pintle is stuck open, the idle speed will remain high. If the pintle is stuck closed, the idle speed will be too low, and
stalling may occur. If the pintle is stuck partially open, the idle speed will be higher than normal, and there will be no response to changes in engine
load such as A/C ("ON") or transmission in ("Drive").
