The positive crankcase ventilation valve of a Toyota Avalon is part of its emissions control system. The PCV valve---as it is commonly called---is secured in a rubber grommet and mounted in the engine's valve cover.
The PCV valve's purpose is to reduce harmful emissions produced by the vehicle by siphoning hydrocarbon vapors back into the intake manifold.
A clogged PCV valve can severely hinder the engine performance. When the PCV valve is clogged, the engine might run rough because the oil does not flow properly, causing sludge to accumulate. Consequently, your engine may stall or refuse to turn over, and oil leaks may develop.
On recent models of Toyota Avalon as of 2011, an OBD II system monitors the condition of the PCV valve. On 2002 and earlier models the PCV valve must be visually checked for damage.
