Positive Crankcase Ventilation: Description and Operation

Positive Crankcase Ventilation System (PCV):

The PCV valve is operated by intake manifold vacuum. When the engine is running at idle, the PCV valve is slightly opened and a small amount of blow-by gas is drawn into the combustion chamber. At higher speeds, the PCV valve is further opened and a larger amount of blow-by gas is drawn into the combustion chamber.