Positive Crankcase Ventilation: Description and Operation

PCV System:

^ The PCV valve is operated by intake manifold vacuum to prevent blow-by gas from escaping to atmosphere.
^ When running at idle, the valve is slightly opened and a small amount of blow-by gas is drawn into the combustion chamber.
^ At higher engine speeds, the valve opens further and a large amount of blow-by gas is drawn into the combustion chamber.