GM S10/S15/Sonoma Pick-Ups 1982-1993 Repair Manual

Engine Speed Oscillates at Idle

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When the engine idle speed will not remain constant, check for the following, as necessary:



A faulty fuel pump.
 
A leaky Exhaust Gas Recirculation (EGR) valve.
 
A blown head gasket.
 
A worn camshaft.
 
Worn timing gears, chain or sprockets.
 
Leaking intake manifold-to-engine gasket.
 
A blocked Positive Crankcase Ventilation (PCV) valve.
 
Overheating of the cooling system.
 
Fault with the computerized engine control system.
 

 
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