Positive Crankcase Ventilation: Description and Operation

Positive Crankcase Ventilation System (PCV):

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