S15/T15 Sonoma P/U 2WD V6-262 4.3L VIN Z TBI (1995)
EGR Valve: Testing and Inspection
With Port EGR Valve
RESULTS OF INCORRECT OPERATION
With too much Exhaust Gas Recirculation (EGR) flow at idle, cruise, or cold operation, any of the following conditions may occur:
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Engine stops after cold start.
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Engine stops at idle after deceleration.
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Vehicle surges during cruise.
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Rough idle.
If the EGR valve should stay open all of the time, the engine may not idle.
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Diagnostic Trouble Code (DTC) PO4OO may set. Refer to Diagnostic Trouble Code Charts. See: Computers and Control Systems/Testing
and Inspection
Too little or no EGR flow allows combustion temperatures to get too high during acceleration and load conditions. This could cause:
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Spark knock (detonation).
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Engine overheating.
SYSTEM CHECK
Diagnosis of the EGR system is covered in Diagnostic Charts/C Charts. See: Computers and Control Systems/Testing and Inspection
