Part of the positive crankcase ventilation system, which reroutes crankcase blow-by to the intake manifold and back to the engine, where it's reburned in the cylinders as part of the fuel/air mixture. This cuts emission pollution and increases fuel economy because unburned fuel in the blow-by is consumed the second time around. It also keeps the blow-by and water vapor from fouling the oil in the crankcase, thus reducing the formation of engine sludge.
The Positive Crankcase Ventilation valve is an emissions control device that routes unburned crankcase blowby gases back into the intake manifold where they can be reburned. The PCV system is one of the oldest emission control devices, and also one of the
The Positive Crankcase Ventilation valve, or PCV valve, is a one-way valve that ensures continual refreshment of the air inside a gasoline internal combustion engine's crankcase.