A crankcase ventilation system is used to
consume crankcase vapors in the combustion
process instead of venting them to atmosphere.
Fresh air from the throttle body is supplied to the
crankcase, mixed with blow by gases and then
passed through a PCV valve into the intake
manifold.

The primary control is through the positive
crankcase ventilation (PCV) valve which meters
the flow at a rate depending on inlet vacuum. To
maintain idle quality, the PCV valve restricts the
flow when inlet vacuum is high. If abnormal
operating conditions arise, the system is
designed to allow excessive amounts of blow by
gases to back flow through the crankcase vent
into the throttle body to be consumed by normal
combustion.
PCV Valve Operation And Description


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