Legacy L Wagon AWD F4-2.2L SOHC (1997)
Positive Crankcase Ventilation: Description and Operation
PURPOSE/OPERATION
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The Positive Crankcase Ventilation (PCV) system is employed to prevent air pollution which will be caused by blow-by gas being emitted from
the crankcase.
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The system consists of a sealed oil filler cap, rocker covers with fresh air inlet, connecting hoses, PCV valve and an air intake duct.
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At the part throttle, the blow-by gas in the crankcase flows into the intake manifold through the connecting hose of crankcase and PCV valve by
the strong vacuum of the intake manifold. Under this condition, the fresh air is introduced into the crankcase through connecting hose of rocker
cover.
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At wide open throttle, a part of blow-by gas flows into the air intake duct through the connecting hose and is drawn to the throttle chamber,
because under this is condition, the intake manifold vacuum is not so strong as to introduce all blow-by gases increasing with engine speed directly
through the PCV valve.
