Auto Parts - What Are the Signs of a Faulty PCV Valve? - New - Blog
Your PCV valve is a tiny part that regulates pressure inside your engine’s crankcase. Despite how small and cheap this part can be, a failing PCV valve can cause a wide range of issues.
What a PCV Valve Does
A PCV valve is a small plastic or metal valve, usually mounted on or near the valve cover on top of your engine, with a hose running to the engine’s intake system.
As your engine runs, small amounts of combustion gas leak past the piston rings, into the crankcase below the engine. If left alone, the gas can pressurize the crankcase and contaminate your engine oil. The PCV valve is a one-way valve that routes the gas back into the engine’s intake, where they are burned along with the normal air and fuel mixture.
If the PCV valve fails, symptoms will be related to your idle quality, oil consumption, and leaking, as well as overall reduced engine performance.
Signs of a Faulty PCV Valve
Watch out for these symptoms, which can indicate your PCV valve has failed:
- Rough or unusually high idle: If the PCV valve sticks open, it can let more air into the intake than the engine computer is expecting, which throws off the mixture of air and fuel while idling. This is sometimes referred to as a “vacuum leak.”
- Whistling or hissing sound: A cracked hose or a valve that’s stuck open can let intake vacuum “leak” through the wrong path, causing an audible whistle, especially while idling.
- Increased oil consumption or an oil leak: If the valve sticks closed, crankcase pressure can build up with nowhere to go, which can force oil through gaskets and seals.
- Check engine light: The engine’s computer monitors airflow and fuel trim. A stuck PCV valve throws these readings off and can trigger the code for a check engine light.
- Blue smoke from the exhaust: If oil is being pulled into the intake from a stuck open valve, it will burn along with the fuel and show up as smoke in your exhaust.
Can You Still Drive With a Bad PCV Valve?
While a failed PCV valve isn’t good for your vehicle’s emissions and oil quality, this isn’t a safety-critical failure like worn brakes. You can technically still drive with a bad PCV valve for a while, but the risk to your vehicle is cumulative. Oil residue or unburned crankcase vapour can build up on intake components, and a stuck valve can cause the engine to run slightly rich or lean over time.
Diagnosing and Replacing the PCV Valve
To conduct this test, ensure the engine is running and warm. Keep hands, hair, and clothing clear of the belts and fan.
Idle the warm engine and remove the oil filler cap.
Hold a piece of paper flat over the opening.
If the paper is pulled down gently, the system is drawing vacuum as it should.
If it’s pushed away or puffing air, the crankcase pressure is too high, a sign of a plugged or stuck-closed valve.
Replace the cap securely.
An OBD scanner can indicate if an error code points to airflow or fuel trim issues consistent with a PCV problem.
Before replacing the old PCV valve, make sure you have protective eyewear and gloves, especially if there are sharp components in the engine bay. Wait for the engine to cool completely and work in a well-ventilated area.
- Pull one end of the PCV valve from the grommet.
- Separate the other end from the hose. If the valve is secured by a hose clamp, use pliers to squeeze the clamp open.
- Replace the hose if it’s clogged or brittle.
- Insert the new PCV valve into the end of the hose and reinstall the hose clamp (if applicable), before pushing the PCV valve back into the grommet.
- Make sure the other end of the hose is properly connected.
For questions about finding the right parts and the proper steps to replace your PCV valve, visit your local NAPA Auto Parts store to speak with an automotive expert or browse our full selection of engine parts at www.NAPACanada.com.
Meta description: Rough idle, oil leaks, or a check engine light? These are common signs of a faulty PCV valve. Learn more about this easy, affordable fix.
