PCV System: Operation
On gasoline models, intake manifold vacuum at idle pulls blow-by vapors through the oil screen, calibrated jet, and into intake manifold. The calibrated jet stabilizes ventilation flow at a rate that will not affect idle mixture. When engine speed and load are high, blow-by exceeds the capacity of the calibrated jet. Intake manifold vacuum is low, but air cleaner vacuum is high enough to pull vapors into air cleaner and through engine.