Positive Crankcase Ventilation Valve: Description and Operation

PURPOSE
The Positive Crankcase Ventilation (PCV) Valve, located top of valve cover, meters air flow in the system at a rate that varies with manifold vacuum. The PCV valve restricts the flow of crankcase emissions when vacuum is high to preserve idle stability.

OPERATION
The PCV valve contains a spring loaded plunger. When the engine starts, the plunger in the PCV Valve is lifted in proportion to intake manifold vacuum and the blow-by gas is drawn directly into the intake manifold.