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How to Tell if a PCV Valve is Bad?

Updated February 21, 2017

The positive crankcase ventilation system is responsible for reducing emissions from the engine. The PCV (positive crankcase ventilation) valve within the PCV engine is a small spring-loaded valve with a sliding pintle inside. The pintle will increase or decrease the airflow to regulate the volume of air passing through the PCV valve. The hose on top of the PCV valve is connected to a vacuum port on the throttle body. The hose allows the vapours to be directed into the engine without building up on the throttle body. It's important that the PCV valve works properly to ensure adequate air to fuel mixture. Check the PCV valve regularly to ensure the system is working efficiently.

Place the vehicle in park and open the bonnet. Locate the PCV valve on the valve cover or intake valley, depending on your vehicle. The valve is seated in a white rubber grommet. Refer to the vehicle owner's manual for exact location.

Turn the vehicle on while keeping the gearshift in park. Allow the engine to run for a few minutes to warm up.

Place a finger over the end of the valve; there should be suction coming from the valve. If there is no suction, the valve or hose is plugged and needs to be replaced.

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About the Author

Johnathan Cronk is a freelance writer and began writing at the age of 18. Throughout his career he has specialized in sports, how-to and advice articles. He has also written sales pitches in the corporate setting since 2001. He studied business at Hudson Valley Community College before transferring to the State University of New York, Albany.