Astro Van L AWD V6-262 4.3L VIN Z (1994)
many flashes in the extend position before engine speed will begin to drop. This is normal on certain engines, fully extending the IAC may cause
engine stall. This may be normal.
3.
Steps 1 and 2 verified proper IAC valve operation while this step checks the IAC circuits. Each lamp on the node light should flash red and green
while the IAC valve is cycled. While the sequence of color is not important if either light is OFF or does not flash red and green, check the circuits
for faults beginning with poor terminal contacts.
IAC VALVE RESET PROCEDURES:
^
With scan tool enter 10K mode.
^
Raise engine speed to 2000 RPM for 5 seconds.
^
Lower engine speed to idle.
Diagnostic Aids:
A slow, unstable, or fast idle may be caused by a non-IAC system problem that cannot be overcome by the IAC valve. Out of control range IAC scan
tool counts will be above 60 if idle is too low, and zero counts if idle is too high. The following checks should be made to repair a non-IAC system
problem.
^
Vacuum Leak (High Idle) - If idle is too high, stop the engine. Fully extend (low) IAC with tester.
Start engine. If Idle speed is above 800 RPM, locate and correct vacuum leak including crankcase ventilation system. Also, check for binding of
the throttle blade or linkage.
^
System Too Lean (High Air/Fuel Ratio) - The idle speed may be too high or too low. Engine speed may vary up and down and disconnecting the
IAC valve does not help. DTC 44 may be set scan O2s voltage will be less than 300 mV (.3 volts). Check for low regulated fuel pressure water in
the fuel or a restricted injector.
^
System Too Rich (Low Air/Fuel Ratio) - The idle speed will be too low. Tech 1 scan tool IAC counts will usually be above 80. System is
obviously rich and may exhibit black exhaust smoke.
Tech 1 scan tool O2s voltage will be fixed above 800 mV (.8 volts).
Check for high fuel pressure, leaking or sticking injector. Silicone contaminated O2s scan voltage will be slow to respond.
^
Throttle Body - Remove IAC and inspect bore for foreign material.
See DIAGNOSIS BY SYMPTOM.
If intermittent poor driveability symptoms are resolved by disconnecting the IAC, carefully recheck connections, valve terminal resistance, or
replace IAC.
^
A/C Compressor or Relay Failure - Refer to A/C Diagnosis if circuit is shorted to ground. If the relay is faulty, idle problem may exist. See
DIAGNOSIS BY SYMPTOM.
