Crankcase Ventilation System Description: Operation
WARNING: This page is about a different car, the 2003 Chevrolet Monte Carlo and 2003 Chevrolet Impala. However, it is still accessible from the selected car via links, so may be relevant.
The primary control is through the PCV valve (1) 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.