Positive Crankcase Ventilation (PCV) system — general information
1. The Positive Crankcase Ventilation(PCV) system reduces hydrocarbon emissions by scavenging crankcase vapors. It does this by circulating fresh air from the air cleaner through the crankcase, where it mixeswith blow-by gases and is then rerouted through a PCV valve to the intake manifold. The PCV system uses intake manifold vacuum to draw crankcase vapors from the crankcase into the intake manifold. The PCV valve varies the number of blow-by gases that can be returned to the intake manifold in proportion to the amount of intake manifold vacuum available, but in the event of a backfire it prevents the entry of combustion gases into the manifold. To maintain idle quality, the PCV valve restricts the flow when intake manifold vacuum is high.
2. The PCV system consists of a fresh-airinlet hose between the air intake duct and the crankcase, the PCV valve itself and the PCV hose (also referred to as the crankcase ventilation hose), which connects the PCV valve to the intake manifold. The PCV valve is attached to a crankcase vent oil separator, located underneath the intake manifold (see illustration). The crankcase vent oil separator acts as a baffle to prevent oil in the crankcase from entering the PCV valve.
i.2 Location of the PCV valve (viewed from above — intake manifold removed)
3. Inspect the fresh-air inlet hose and thePCV valve hose (crankcase ventilation hose) for cracks, leaks and other damage. Disconnect the hose from the crankcase vent oil separator and the intake manifold and check the inside for obstructions. If a hose is clogged, replace it. If the PCV valve is clogged or otherwise not working properly, replace it — do not try to clean it.
4. PCV valve replacement is covered in Tune-up and routine maintenance.