How To Test A PCV Valve: [Easy Guide]-Sincere Mechanic

The Positive Crankcase Ventilation (PCV) system consists of a PCV valve, a hose, and a vacuum source, usually from the intake manifold. It performs a crucial role in maintaining the engine’s health by regulating and redirecting the harmful gases produced during fuel combustion to the intake manifold, where these gases are burned, which keeps the combustion process smooth and efficient. 

Over time, the PCV valve can become clogged, stuck open, stuck-closed, or malfunction, resulting in several engine performance issues and reducing vehicle efficiency. Periodically testing the PCV valve as part of regular maintenance schedule services will keep the vehicle’s engine safe from critical issues.

In this guide, we will go over how to test a PCV valve, prepare the tools you’ll need to check & replace the valve, and, discuss other important things to know while testing the valve.

Why Test the PCV Valve?

While the PCV valve test is crucial, if it’s not checked regularly and left unchecked, then the bad PCV valve can cause a variety of engine problems that are breakdown below:

Poor fuel economy: 

When the PCV valve is stuck open and not functioning as it should, it can cause a lean air-fuel mixture (too much air and insufficient fuel), resulting in increased fuel consumption and poor fuel economy.

Oil contamination: 

A blocked or clogged PCV valve fails to redirect the useless vapors, which will result in sludge formation in the crankcase. Due to unburned vapors, the oil can become contaminated, which might impact the overall engine performance.

Rough idle or stalling: 

A faulty PCV valve can cause an imbalance in the air-fuel ratio. Due to excessive air and low fuel, your vehicle might behave roughly or start stalling during acceleration.

That’s why, to prevent these issues, you must learn to check a PCV valve and inspect it for any wear or signs of damage.

Signs of a Faulty PCV Valve

Here’s the breakdown of the most common bad PCV valve symptoms that will help you when testing and finalizing whether the valve needs replacement.

• Rough engine idle
• Hissing noises from the engine
• Illumination of check engine light (often triggered by incorrect airflow)
• Engine misfiring
• Oil leaks or fouled spark plugs
• Increased oil consumption
• Poor acceleration or performance

If you experience more than one sign, you must promptly test the PCV valve to overcome occurring issues.

Tools Needed to test PCV valve

It’s a wise approach to prepare the tools needed to check the PCV valve as it’s a DIY task that can be performed easily without going to the mechanic shop, which might charge an extra service cost.

• Screwdriver (if you need to remove engine covers)
• Wrench or socket set (if necessary, depending on how the valve is mounted)
• Needle-nose pliers (for removing clamps)
• A New PCV valve (if the old valve is faulty and needs to be changed)
• Vacuum gauge (optional but useful for performance testing)

How to test a PCV valve?

There are three different methods to test a PCV valve. You can follow each step-by-step method and complete the valve testing.

Visual inspection

The first and easy-to-proceed method is visually inspecting the PCV valve to look for any signs of damage, wear & tear, or blockage. The steps below will guide you in taking a practical test.

• Locate the PCV valve: However, the exact location of the valve can vary depending on the car model and the year. Usually, it’s located near the rubber hose, which connects the valve cover with the intake manifold. Its common locations include near the throttle body, on or near the valve cover, and connected to the manifold.
• Remove the valve: After successfully locating the valve, the next step is to detach it from the hose and remove it with the help of a wrench or pliers.
• Shake the valve: You might see the PCV valve dirty and cruddy, but that’s not a bad sign. Start shacking the valve and focus on hearing a solid metallic sound that is produced due to the insider spring-loaded plunger that should move freely when you shack.
• If the valve rattles: If you hear a solid metallic sound, the PCV valve is likely in good working condition.
• If no rattling sound: If no sound is produced while shacking the valve, it means the valve is clogged, stuck-open, or closed and needs replacement.

Testing with Suction

The second way to learn how to test a PCV valve is through suction, described below.

• Start the engine and keep it running for a few minutes.
• Carefully remove the valve from the cover while keeping it connected to the hose for testing.
• Place your finger over the valve’s opening.
• The valve functions correctly if you feel strong suction while placing the fingers.
• The valve may be clogged or malfunctioning if there is little or no suction.

Note: Be careful while performing this method for the PCV valve test, as the engine might be hot after idling.

Vacuum Gauge Test (For Advanced Diagnosis)

A vacuum gauge test is a more precise and advanced way of performing how to check a PCV valve task. This method is especially useful if you know how to test a PCV valve without removing it. Here’s how you can conduct a diagnosis, which is mentioned below.

• First, connect the vacuum gauge to the intake manifold or the PCV valve.
• Check the readings: A healthy PCV valve will show a vacuum level consistent with your vehicle’s specifications (typically between 18 and 22 inHg idle).
• Low or erratic readings: If the readings are inconsistent and lower than the minimum level of 18 Hg, the PCV valve has become faulty or clogged.

How to Replace a PCV Valve: Step-by-Step Guide

If you find that the PCV valve is faulty and can’t be used anymore, it’s time to replace the faulty one with a new one, which is quite a simple & quick task to perform and can be done in under 30 minutes.

1. Locate the PCV Valve: Find the PCV valve, usually near the rubber hose.
2. Remove Engine Covers: If the PCV valve is covered with an access-blocking engine cover, remove it with a wrench or screwdriver to access the valve.
3. Disconnect the Hose: Use pliers to loosen the hose clamp and disconnect it from the valve.
4. Remove the PCV Valve: If the PCV valve is threaded, use a socket wrench to unscrew it. If it’s a push-in type, pull it out by hand or with pliers.
5. Install the New PCV Valve: Insert the new PCV valve and ensure you’re not ovetighting it as it might affect it later.
6. Reconnect the Hose: Reattach the hose to the new valve and secure it with the clamp.
7. Reinstall Any Engine Covers: You can now reattach any cover if you remove it before replacing the PCV valve.

Final check

Conduct a final check to ensure everything is done accurately by starting the engine. Look for hissing noises, vacuum leaks, or wear pointing to bad replacement. If no such signs exist, you have done it correctly and can enjoy a smooth driving experience.

Also Read: Symptoms Of A Bad Drive Shaft
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Wrapping up

To keep your vehicle running smoothly and efficiently, it is crucial to maintain each small and large component of the vehicle. One such significant part is the PCV valve, which might lead to several issues if it becomes faulty or starts malfunctioning. After understanding how to test a PCV valve by following simple visual checks, suction tests, or vacuum gauge tests, you can easily detect a bad valve and replace it accordingly, which protects your engine from critical issues such as rough idling, misfires, and increased fuel consumption.