Positive Crankcase Ventilation Valve: Description and Operation

PCV Valve:

OPERATION
The Positive Crankcase Ventilation (PCV) valve is a flow control valve that regulates vapor flow. When the engine idles and vacuum is high, the plunger in the PCV valve is pulled to a nearly closed position so that vapor flow is light and does not upset the air-fuel mixture. As the throttle is opened, vacuum drops and a spring pushes the valve open, allowing more vapor to flow when the engine can better accept it.