PCV system (see accompanying illustration) serves to reduce the emission of hydrocarbon compounds into the atmosphere due to the removal of crankcase gases from the engine. The unit is purged by forcing fresh air coming from the air cleaner through the crankcase, where it mixes with accumulated fumes and gases escaping from the combustion chambers and is discharged through the PCV valve into the intake manifold.
The main components of the system are the PCV valve, the purge filter and the set of vacuum hoses connecting these devices to the engine.
In order to maintain stable idle speed, the PCV valve shuts off the purge flow when the vacuum in the intake manifold is deep. In the event of a malfunction of the engine (such as worn piston rings) the system removes excess crankcase gases through the ventilation tube back to the air cleaner.