How to Test a PCV Valve


There are a variety of components in the emission control system of modern automobiles, one of which is the positive crankcase ventilation (PCV) valve. This is a one-way valve which helps remove gases from the engine crankcase and increases the engine's efficiency, thereby reducing exhaust pollutants. A PCV valve that is not operating properly can have a negative impact on engine performance. Checking the PCV valve for proper operation is something which many car owners can do themselves.

Things You'll Need

  • Pliers
  • Park the car, set the parking brake and open the hood.

  • Locate the PCV valve and the rubber hose connected to it. This is a small, cylindrical component 2 inches long by 1 inch in diameter, with a connector for the hose on the top of it. Typically, the PCV valve will be mounted onto the valve cover at the top of the engine.

  • Start the engine. Pinch the hose going to the PCV valve with pliers to block the air flow inside the hose. If the valve is operating properly, the engine idle speed should decrease. If the engine continues to idle at the same speed, PCV valve replacement is necessary.

Tips & Warnings

  • Avoid contact with all moving parts while doing this test.

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  • Photo Credit engine image by goce risteski from
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