Silhouette V6-191 3.1L VIN D TBI (1995)
Positive Crankcase Ventilation: Description and Operation
PCV Valve (Typical)
PCV Flow (Typical)
A crankcase ventilation system is used to consume crankcase vapors in the combustion process instead of venting to atmosphere. Fresh air from the air
cleaner is supplied to the crankcase, mixed with blow-by gases and then passed through a crankcase ventilation valve into the intake manifold.
The primary control is through the valve which meters the flow at a rate depending on manifold vacuum.
To maintain idle quality, the crankcase ventilation valve restricts the flow when intake manifold 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 tube into the air cleaner to be
consumed by normal combustion.
A leaking valve or hose would cause:
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Rough idle.
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Stalling.
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High idle speed.
