Q: What is the function of the Positive Crankcase Ventilation (PCV) system and PCV Valve?
A: The PCV system consists of a PCV valve, a fresh air-filtered inlet, and vacuum hoses. The PCV valve restricts flow when the intake manifold vacuum is high, but allows excessive blow-by gases to flow back into the air cleaner under abnormal conditions. Fuel-injected vehicles use a Crankcase Ventilation System (CCV) that doesn't use a vacuum-controlled valve. Instead, it uses a molded vacuum tube connected to a grommet on the rocker arm cover, which contains a calibrated orifice that meters crankcase vapors. A new air supply hose from the air cleaner is attached to the rocker arm cover, allowing fresh air to mix with the crankcase vapors and be consumed during combustion.