G 20 Van V6-262 4.3L VIN Z TBI (1995)
Idle Speed/Throttle Actuator - Electronic: Testing and Inspection
The diagnosis of Idle Air Control (IAC) valve can be found in System Diagnosis / C-Charts. See: Computers and Control Systems/Testing and
Inspection
IAC RESET
If the IAC valve is disconnected or connected with the engine running, the idle RPM may be wrong. The IAC valve may be reset by disconnecting
negative battery terminal for 10 seconds then reconnect battery cable, turn key "ON," engine "OFF" for 5 seconds then turn key "OFF" for 10
seconds.
SYMPTOMS
The IAC valve affects only the idle characteristics of the engine. If it is open fully, too much air will be allowed in the manifold and idle speed will
be high. If it is stuck closed, too little air will be allowed in the manifold, and idle speed wilt be too low. If it is stuck part way open, the idle may
be rough, and will not respond to engine load changes.
System too lean (High air / fuel ratio)
Idle speed may be too high or too low. Engine speed may vary up and down, disconnecting IAC does not help. May set DTC 44.
Scan tool and/or voltmeter will read an oxygen sensor output less than 300 mV (0.3 volt). Check for low regulated fuel pressure or water in fuel. A
lean exhaust with a Heated Oxygen Sensor (HO2S) output fixed above 800 mV (0.8 volt) will be a contaminated sensor, usually silicone. This may
also set a DTC 45.
System too rich (Low air / fuel ratio)
Idle speed too low. Scan counts usually above 80. System obviously rich and may exhibit black exhaust smoke. Scan tool and/or voltmeter will
read a Heated Oxygen Sensor (HO2S) signal fixed above 800 mV (0.8 volt).
