The PCV system (see accompanying illustration) serves to reduce the emission of hydrocarbon compounds into the atmosphere by removing crankcase gases from the engine. The block is purged by passing fresh air from the air cleaner through the crankcase, where it mixes with accumulated vapors and gases that have broken through from the combustion chambers and is removed through the PCV valve into the intake manifold.
The main components of the system include the PCV valve, purge filter, and a set of vacuum hoses that connect these devices to the engine.
To maintain stable idle speed, the PCV valve closes the purge flow when there is a deep vacuum in the intake manifold. In the event of a malfunction of the engine (such as when the piston rings wear out), the system removes excess crankcase gases through the ventilation tube back to the air cleaner.
For a description of the PCV valve inspection and replacement procedures, see Section Checking and replacing the PCV valve.
(Article source on the website HondaBook.ru)