Top 8 Bad PCV Valve Symptoms

Bad PCV Valve

Cars are complex machines requiring many different parts to work in tandem to run smoothly. When it comes to the engine, one of the most critical components is the PCV valve.

For those unfamiliar with automotive jargon, PCV stands for positive crankcase ventilation. Essentially, this valve regulates the flow of gases within the engine and allows for the safe and efficient operation of the car.

The PCV valve may seem small and insignificant, but it plays a crucial role in maintaining the engine's health and overall performance. Harmful gases can accumulate in the engine without a properly functioning PCV valve and cause significant damage.

Unfortunately, many car owners are unaware of the symptoms of a bad PCV valve, which can lead to severe problems down the line.

In this article, we'll discuss the function of the PCV valve and why it's crucial for your car's engine. We'll also explore all the bad PCV valve symptoms and what to do if you suspect yours needs attention.

What Are the Functions of PCV Valve?

The PCV valve is an integral part of the Positive Crankcase Ventilation system, used in modern automobiles to regulate the pressure within the engine. The engine produces pressure from oil churning by moving parts, and the PCV valve helps to vent this pressure and perform other essential tasks.

The PCV system consists of several components, including the PCV valve, tube, grommet, and hose for supplying air to the crankcase. The PCV valve is typically located on the valve cover of most engines.

However, in some models, it can also be found on a hose between the valve cover and the air intake filter or integrated with the valve cover. To locate the PCV valve, open the hood and follow the hose on the top of the engine.

Most PCV valves are constructed similarly, with two hosing connectors and a spring-loaded one-way valve inside.

The valve works by regulating the flow of gases from the crankcase to the intake manifold, which helps control the engine's pressure. By controlling the pressure, the PCV valve helps to prevent oil leaks, reduce engine emissions, and increase fuel efficiency.

The PCV valve plays a critical role in maintaining the health and performance of the engine, and car owners need to understand how it works and how to recognize signs of a malfunctioning PCV valve.

Bad PCV Valve Symptoms

You must watch for bad PCV valve symptoms if you're a car owner. This valve is crucial to the engine's Positive Crankcase Ventilation system.

When it's not working correctly, it can cause various issues. Here are some common symptoms of a bad PCV valve:

1. Rough Idle

When the PCV valve is faulty, it can cause the engine to vibrate and shake while idling.

This is often due to an incorrect air-to-fuel ratio, resulting in poor engine performance and reduced fuel efficiency.

2. Misfiring While Idling

A bad PCV valve can also cause the engine to misfire, along with a rough idle.

This can be due to an irregular spark plug firing, which can cause a stuttering or sputtering sound from the engine.

3. Engine Light Warning

A malfunctioning PCV valve can trigger the check engine light to come on.

This warning light can indicate a range of issues, so a professional must check your vehicle to determine the exact cause of the warning.

4. Noise From the Engine

If you hear a high-pitched whistling or hissing sound coming from the engine, it could be due to a bad PCV valve.

This is caused by the valve not regulating the flow of gases properly, which can increase engine noise.

5. Rough Acceleration

Another sign of a bad PCV valve is rough acceleration. When the valve is not functioning correctly, it can cause a delay in the engine's response time, resulting in sluggish acceleration and poor overall performance.

6. Smoke From the Exhaust

A bad PCV valve can also cause smoke to come out of the exhaust. This is due to an increase in oil consumption, which can cause oil to leak into the engine's combustion chamber and be burned along with the fuel.

7. Oil Leaks

Speaking of oil leaks, this is another common symptom of a bad PCV valve. When the valve is faulty, it can cause a buildup of pressure in the engine, resulting in oil leaks from various parts of the engine.

8. Engine Running Lean/Rich & Poor Fuel Economy

A bad PCV valve can cause the engine to run either too lean or too rich. This can result in poor fuel economy, as the engine is not operating optimally.

How To Test Your PCV Valve

If you're experiencing issues with your vehicle and suspect that the PCV valve might be the culprit, it's crucial to test the valve to confirm its functioning properly.

Thankfully, testing a PCV valve is a relatively simple process that can be done at home. You can take a few steps to test your PCV valve and ensure it's in good working condition.

First, inspecting the PCV valve grommets is crucial to ensure they are in good condition. Grommets can become damaged over time due to wear and tear, leading to leaks and other issues.

Look for signs of cracking, damage, or wear on the grommet, and replace it if necessary.

Next, inspect the PCV valve hoses to ensure they are not damaged or cracked. These hoses play an essential role in the positive crankcase ventilation system, and any damage can lead to leaks or improper functioning. Make sure the hoses are correctly connected and securely in place.

Another essential step in testing your PCV valve is to check for moisture contamination. Over time, the valve can become clogged or contaminated with moisture, which can cause it to malfunction.

Remove the PCV valve and shake it gently to check for moisture contamination. If you hear a rattling sound, the valve is functioning properly. If you don't hear a sound, or if the sound is muffled, the valve may be clogged and need to be replaced.

If you still need to determine whether your PCV valve is functioning correctly, you can also try blowing through it in the direction of the intake manifold. If air passes through quickly, the valve is working correctly.

If it's difficult to blow through or air does not pass through, the valve may be clogged and need to be replaced.

Testing your PCV valve is essential in ensuring your vehicle's proper functioning.

By following these simple steps, you can diagnose any issues with your PCV valve and take the steps needed to keep your engine running smoothly.

How Much Does It Cost To Replace a PCV Valve?

If you're experiencing issues with your PCV valve, how much will it cost to replace it? The cost of a PCV valve replacement can vary depending on a few factors.

The average price falls between $50 and $250. It's important to note that the final cost will depend on your vehicle's make and model and the labor costs in your area.

When it comes to the actual cost of the PCV valve itself, most designs fall within the range of $20 to $50.

However, the labor cost can vary greatly depending on the job's complexity. If your vehicle is an older model and the PCV valve is easily accessible, the replacement process may only take 10 minutes, with labor costs ranging from $30 to $100.

However, the PCV valve may be under the intake manifold for newer cars. This can make the replacement process more time-consuming and difficult, potentially taking up to 3 hours to complete.

Labor costs in these cases can range from $100 to $200, increasing the total cost of the replacement.

It's also worth noting that the cost of a PCV valve replacement may not include any additional repairs necessary during the inspection.

For example, if there is damage to the valve cover gasket or vacuum hoses, these will also need to be replaced, adding to the overall cost of the repair.

While the cost of a PCV valve replacement may seem daunting, addressing any issues with your vehicle as soon as possible is essential. Ignoring problems with the

PCV valve can lead to more severe cases down the line, potentially causing significant damage to your engine.

In the long run, investing in a PCV valve replacement can ensure the longevity and reliability of your vehicle.


A malfunctioning PCV valve can cause a wide range of issues with your vehicle, from rough idling and misfiring to poor fuel economy and oil leaks.

By knowing all the bad PCV valve symptoms and testing it regularly, you can take the necessary steps to keep your engine running smoothly.

If you suspect that your PCV valve is not functioning correctly, it's essential to have it inspected by a professional mechanic. They can help diagnose any issues and recommend the best course of action for replacement.