A positive crankcase ventilation valve. It uses vacuum from the intake manifold to draw fumes from the crankcase. Symptoms of a faulty PCV valve are poor idle and excessive pressure in the crankcase.

An emissions control device that allows gases from the crankcase to be reintroduced into the intake.

A valve usually located in the rocker cover that vents crankcase vapors back into the engine to be reburned.

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.