You’ve probably heard of the PCV valve if you drive a gas or petrol-powered car, but you might not realize just how crucial this small component is to your engine’s health. Despite its simple design, the PCV valve often fails, and it’s a common issue in many petrol engines on the road today.
Most PCV valves are made of plastic with a small spring inside. Over time, the heat from the engine bay causes the plastic to wear out, especially after years of use. Because the valve plays such an important role in regulating crankcase gases, you’ll likely notice a few bad PCV valve symptoms when it starts to fail.
In this guide, we’ll cover the most common signs of a faulty PCV valve, how it affects your engine, and what you can expect when it’s time for a replacement. Let’s get started.
Signs of a Bad PCV Valve
The most common symptoms of a bad PCV valve include a rough idle, poor engine performance, and the Check Engine Light appearing on your dashboard. You might also notice increased oil consumption or blue smoke coming from the exhaust.
These bad PCV valve symptoms can lead to more serious engine problems if ignored, so it’s important to address them early.
1. Check Engine Light
One of the most common and most noticeable bad PCV valve symptoms is probably the check engine light on your dashboard. When the engine light shows up, there is a trouble code stored in the engine control module.
To read the trouble code from the engine control unit, you have to use an OBD2 scanner. Some older cars with a PCV valve fitted without an electronically controlled engine will not have this symptom.
2. High Idle RPM/Rough Idle
Because the PCV valve controls the airflow between the crankcase and the intake manifold, a broken PCV valve can have the same symptoms as an intake air leak, which can cause the idle RPM to get too high and other strange idle behaviors like a very rough idle.
If you have any strange idle problems, it’s always a good idea to check the PCV valve first.
3. Lean/Rich Mixture
Because of the issues discussed, a faulty PCV valve can have the same symptoms as an intake leak, and the air/fuel mixture can end up being wrong. Usually, your air/fuel mixture will become lean, and you can feel the same symptoms as from a lean mixture.
With a rich mixture, you can often see that the car has a little more gray/white smoke than usual, and you can often detect the smell of petrol.
Lean mixture is more difficult to find, but it often causes misfires, as we will discuss next.
4. Misfires
Because you can get a faulty lean/rich mixture due to a faulty PCV valve, you might feel misfires while idling or accelerating when your PCV valve is bad.
If you have a too lean mixture, the cylinders won’t fire up correctly, which can cause misfires. If you have a mixture that is too rich, you can turn off the spark with the fuel and therefore cause a misfire.
5. Rough Acceleration
When you have a faulty PCV valve causing a wrong fuel mixture, you can feel that your car has rough acceleration on high and low RPMs.
On most cars, you won’t feel a broken PCV valve on higher RPMs than idle, but it’s worth mentioning because it can happen depending on the valve’s design.
6. Increased Oil Consumption & Oil leaks
If the PCV valve or the hoses are blocked by moisture, you will get a very high pressure inside the engine crankcase, which will push the pressure up in the cylinders and out from the gaskets.
If you suddenly see several large oil leaks and increased oil consumption in your car, check the PCV valve and the hoses to it to make sure they’re not blocked.
7. White/Black/Blue Smoke from the Exhaust
If the PCV valve or the hoses are blocked, the crankcase will push oil up into the combustion chambers, which will cause oil to burn inside the engine and go out through the exhaust pipe.
This will cause a lot of blue smoke from the exhaust pipe. If the PCV valve is faulty and causing a rich or lean mixture to the engine, you can get symptoms like white or black smoke coming out from the exhaust pipe, depending on what type of mixture problem the engine has.
A short conclusion is: If you see any strange smoke from the exhaust pipe, make sure that the PCV valve is in good shape.
What is a PCV Valve?
PCV valve stands for Positive Crankcase Ventilation, and it is one of the oldest and most used emission devices in many vehicles. The PCV valve’s function is to eliminate crankcase emissions from the crankcase and send them to the intake. The emissions are combusted again in another engine cycle, making the engine’s emissions cleaner and more efficient.
Most PCV valves are made the same way; two hosing connectors with a spring-loaded one-way valve inside. When the engine is idle, you have a lot of vacuum inside the intake manifold, which helps the emissions get sucked out from the crankcase efficiently at lower speeds.
When you are revving up your engine and driving on higher RPMs, the PCV valve will open further and suck out even more crankcase ventilation caused by higher RPM and faster crankcase pressure build-up.
- Idle/Low RPM: High Vacuum, PCV Valve Half Closed
- Higher RPMs: Lower Vacuum, PCV Valve Open Fully
- Backfire from crankcase: PCV Valve Closing
If you have a turbocharged engine, you do not want to boost pressure to go into the crankcase, which would cause oil leaks and blow gaskets. Here, it’s crucial to have a one-way PCV valve.
These valves are designed differently, and the PCV valve only works on idle and low RPMs. Some PCV valves also have three connectors for a vacuum, which controls them with electric vacuum solenoids. These can work in a lot of ways, and we will discuss them in another article.
Common Trouble Codes Associated with the PCV Valve
Some common trouble codes appear with a faulty PCV valve. If you experience any of these trouble codes from your engine control unit, it’s probably time to check the PCV valve.
Remember that just because you see these trouble codes, that doesn’t necessarily mean that the PCV valve is broken. These codes can also be other things, and I always recommend you carry out proper troubleshooting before replacing any parts.
- P052E – Positive Crankcase Ventilation Regulator Valve Performance
- P0171 – Fuel System Too Lean (Bank 1)
- P0300 – Random/Multiple Cylinder Misfire Detected
- P053A Positive Crankcase Ventilation Heater Control Circuit /Open
PCV Valve Location
The PCV Valve is often located on the valve cover, on the top of the engine, but it can also be on a hose between the valve cover and the air intake filter.
Just follow the hose on the top of the car engine, and you will find the PCV valve. Some cars do also have an integrated PCV valve with the valve cover.
PCV Valve Replacement Cost
The average PCV valve replacement cost is between $50 and $250, depending on the car model and labor costs. A PCV Valve mostly costs between $20 and $50. The labor cost is between $30 and $200 at a mechanic workshop.
The replacement cost of faulty PCV valves can differ significantly depending on the engine and the car you have. However, the PCV valve’s price is often meager, and you can expect prices of around $20-50 for a brand-new valve.
If you think you have the knowledge to replace the valve yourself, you will not suffer from the labor costs, but remember that it can be difficult to replace it if it’s located under the manifold on some cars.
If you want a mechanic to replace it for you, you can expect a labor cost of $30-200, depending on the location and the car type.
If you have an older car, the PCV valves are often easy to replace and should only take around 10 minutes, while on newer cars, there could be a replacement time of over 3 hours if it’s located under the intake. Sometimes, you have to remove the intake to access the PCV valve; luckily, this is not very common.
FAQs
If your PCV valve is clogged, you can definitely clean it. But usually, the spring mechanism inside the PCV valve gets old and bad. PCV valves are often quite cheap, so while you can clean it, we recommend replacing it to avoid problems in the near future.
Yes. Without the PCV valve, there may be too much underpressure in the crankcase during idle and too much overpressure in the crankcase during turbo boost. Additionally, the PCV valve also helps to improve fuel efficiency by recycling unburned fuel vapors back into the combustion chamber.
The PCV valve is supposed to be closed or semi-closed during idle so as not to create too much vacuum inside the crankcase. When you press the throttle a little, the PCV valve opens fully to evacuate the crankcase gases.
There is no schedule for when the PCV valve should be replaced. Often the PCV valve will last over 100,000 miles. However, the PCV valve is quite cheap and often quite easy to replace, so if your car is a couple of years old, you may want to replace the PCV valve.
Conclusion
As you can see, most of the symptoms are engine performance problems, which could also be caused by other issues, so it’s important to research the subject carefully.
If you notice any symptoms of a bad PCV valve in your vehicle, it’s time to take it to a mechanic and have them check your PCV valve. It’s a small part that plays a big role in keeping your engine healthy, so don’t wait too long to replace it if it needs fixing. Doing so will keep your car running smoothly for years to come!
Learn more:
- 10 Causes of Car Engine has Rough Idle (How to Fix it)
- White Smoke from Exhaust – Common Causes & How to Fix it
- Check Engine Light Flashing? (Here’s What to Do)
Is it common that after replacing a bad pvc valve which was causing oil consumption that the engine have some white smoke when first started but then fades away ?
I have 2009 Toyota innova D4d, There is oil on intake side of turbo, does worn PCV valve has something to do with this?
Hi bro
My name is Eric. I have bought a second hand Volkswagen Tiguan 1.4 TSI engine type CAVA since November 2019. Two day after having purchased the car I noticed that there is white smoke coming out of the exhaust pipe that last for about 20 seconds in the morning and evening when i return back home (about 10 hours at rest). I have it inspected by 3 mechanics and all have come to the conculusion that there is lack of compression and missfires in at lest one cylinder. Grateful if you could provide advise to what may be the cause of these symptoms. Thanking you for your support.
M Y husband has a 2008 BMW. My question is can a bad PVC heater valve cause frothing or condensation Under the oil cap? Thank you!
Hi! I drive Audi a 4 b 8 2013 with CVT gearbox! And have an issue: the engine starts only from second attempt when it is hot weather (first attempt doesn’t gathering cold rpm’s – 1200, but only 600-400, second attempt is always ok). And another one: when in traffic or parking always pressing the brakes rpms are dropping down for one second. No check engine! Idle rpms are ok -800, dropping only when operating with brakes! Any ideas?! Thanks in advance!
I have a 1995 Honda Civic DX car with a 4 cylinder and 1.6 Liter engine. My mechanic told me that the PCV Valve Cover tube is leaking a small amount of oil and to replacement cost with his labor will cost me a total of $200.00.
Can you tell me if this is a fair price to pay and also should I get the PCV Valve Cover and Hose replaced as soon as possible? What kind of damage will be done if I don’t get the PCV Valve Cover and Hose replaced?
Thank you,