Grand Prix V6-204 3.4L DOHC (1992)
Idle Speed/Throttle Actuator - Electronic: Description and Operation
Idle Air Control Valve Assembly (IAC)
PURPOSE
The purpose of the Idle Air Control Valve (IAC) valve is 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 measured 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 and out to
close and open the idle air passage. The valve is moved in small increments called "COUNTS". Its position can be determined by reading the IAC
"counts" with a "SCAN" tool. Inward Movement of the pintle = Decreased RPM = Lower Counts. Outward Movement of the pintle = Increased RPM
= Higher Counts. The ECM 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 turning A/C "ON", or placing transmission in a drive gear (vehicles
w/automatic trans).
