The PCV valve is designed to control the volume of crankcase vapors entering the engine intake manifold. The PCV valve has a spring-loaded mechanism that opens in response to positive intake manifold vacuum. As the intake manifold is under vacuum, vapors are pulled from the valve cover into the combustion chamber. On SOHC four-cylinder engines, it is located on top of the valve cover, while on DOHC four-cylinder engines, it is threaded into the right rear, and on the V6, at the end of the valve cover. To see how it functions, remove the valve with the hose still attached. If you have a DOHC engine, detach the hose first. You know, after starting up the engine, give a keen hear for a hissing sound coming out from the valve. The moment you hear this, put your finger over the opening to feel if vacuum is present. A vacuum will be present if everything is working fine and the engine is idling. If there is no vacuum check for blocked hoses or ports and replace any damaged parts. Also, use a small screwdriver to push the spring-loaded valve to check whether it returns to its seat. Otherwise, it may be sluggish and contaminated, which implies a replacement is necessary. When you buy a new PCV valve, it must match the vehicle and engine size of your car. Compare it with old PCV valve. The reverse procedure of removal is installation.