Spectrum 3.0L GM - Page 50

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CRANKCASE VENTILATION SYSTEM INSPECTION/DIAGNOSIS
RESULTS OF INCORRECT OPERATION
A plugged positive crankcase ventilation (PCV) orifice or hose may cause the following conditions:
 Rough or unstable engine speed
 Stalling or low idle speed
 Oil leaks
 Oil in the air cleaner
 Sludge in the engine
A leaking PCV orifice or hose may cause the following problems:
 Rough or unstable engine speed.
 Stalling
 High idle speed
Functional check:
Any blow-by in excess of the system capacity, from a badly worn engine, sustained heavy load, etc., is exhausted
into the air cleaner and is drawn back into the engine.
Proper operation of the crankcase ventilation system depends on a sealed engine. If irregular oil flow or dilution is
noted and the crankcase ventilation system is functioning properly, check the engine for another possible cause.
Correct any of these problems first.
If an engine is idling rough, inspect for a clogged PCV orifice, a dirty vent filter, air cleaner element, or plugged
hose. Replace any faulty items found. Use the following procedure:
 Remove the PCV hose (positive side) from the rocker arm cover.
 Operate the engine at idle.
 Place your thumb over the end of the hose in order to check for vacuum. If there is no vacuum at the hose end,
inspect for the following items:
 Plugged hoses
 The manifold vacuum port
 Turn the engine OFF.
 Inspect the PCV orifice in the valve cover for debris or blockage.