PCV System: Operation
When engine is running at idle, high intake manifold vacuum pulls blow-by gases out of breather chamber through PCV valve and into intake manifold where they mix with incoming air/fuel mixture. Fresh air enters crankcase from hose to valve cover.
When engine is running at wide open throttle, manifold vacuum at PCV valve decreases and vacuum in air cleaner increases. As a result a small amount of blow-by gas flows out of the breather hose and into air cleaner.