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

Engine Speed Oscillates at Idle


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.