A crankcase ventilation system is used to consume the crankcase vapors in the combustion process instead of venting the vapors to the atmosphere.

Fresh air from the throttle body is supplied to the crankcase, mixed with the blow-by gases, and then passed through a crankcase ventilation valve into the intake manifold.

The primary control is through the crankcase ventilation valve (1) which meters the flow at a rate dependent upon the inlet vacuum. To maintain the idle quality, the crankcase ventilation valve restricts the flow when the inlet vacuum is high. If abnormal operating conditions arise, the system is designed to allow excessive amounts of blow-by gases to backflow through the crankcase vent into the throttle body to be consumed by normal combustion.