PCV System: Operation

When engine is running at idle, high intake manifold vacuum pulls blow-by gases out of crankcase through PCV valve and into intake manifold where they mix with incoming air/fuel mixture. Fresh air enters crankcase from hose to valve cover on Civic and Prelude, and from hose to breather chamber on Accord.

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 crankcase and into air cleaner.

Fig 1: Crankcase Ventilation System (Accord - Except SEi Models)

Fig 2: Crankcase Ventilation System (Accord SEi)

Fig 3: Crankcase Ventilation System (Civic - Except CRX)

Fig 4: Crankcase Ventilation System (Civic CRX)

Fig 5: Crankcase Ventilation System (Prelude)