Astro Van L AWD V6-262 4.3L VIN Z (1994)
Idle Air Control (IAC) System Check
Circuit Description:
The control module controls idle RPM with the IAC valve. To increase idle RPM, the control module moves the IAC valve away from its seat, allowing
more air to pass by the throttle plate. To decrease RPM, it moves the IAC valve toward its seat, reducing air flow by the throttle plate. A Tech 1 Scan
tool will read the control module commands to the IAC valve in counts. The higher the counts, the more air allowed (higher idle). The lower the counts,
the less air allowed (lower idle).
Test Description: Numbers below refer to circled numbers on the diagnostic chart.
1.
The IAC tester is used to extend and retract the IAC valve. Valve movement is verified by an engine speed change. If NO change in engine speed
occurs, the valve can be retested when removed from the throttle body.
2.
This step checks the quality of the IAC movement in Step 1. Between 700 RPM and about 1500 RPM, the engine speed should change smoothly
with each flash of the tester light in both extend and retract. If the IAC valve is retracted beyond the control range (about 1500 RPM), it may take
