You might have heard of the PCV valve in a gas engine but likely don’t know how important this small plastic piece is to the engine itself. This small piece has a known history of failure and the issue will often occur in most available gasoline engines.
Most PCV valves are plastic hoses with a working spring internal to the plastic hose. All plastic will eventually wear out when used for ten years, particularly permanently affixed in a hot engine bay, and for PCV valve to accomplish its essential function.
You might notice any of these symptoms of a bad PCV valve when it has failed. So, what are the symptoms of a bad PCV valve?
The most common symptoms of a bad PCV valve include a rough idle and engine performance issues, along with a check engine light on your dashboard. You also might see increased oil consumption and blue smoke coming from the exhaust.
Fortunately, this will be discussed further in this article as well as everything you need to know to replace the PCV valve cost. Let’s talk about the symptoms first.
What is a PCV Valve?
PCV stands for Positive Crankcase Ventilation, which is one of the oldest and most used emissions devices in many vehicles.
PCV valves’ job is to take crankcase emissions from the crankcase and put them into the intake. The emissions will be combusted again in the next engine cycle making the engine’s emissions cleaner and more efficient.
Most PCV valves have the same functionality; two hosing connectors with a spring-loaded one-way valve inside.
When the engine is at idle, you have a lot of vacuums inside the intake manifold, which helps the emissions get sucked out of the crankcase efficiently at a lower speed.
When you rev the engine and drive at higher RPMs, the PCV valve will open more and suck even more crankcase ventilation due to increased RPMs 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 any boost pressure to enter the crankcase as it would cause oil leaks and blow gaskets; having a one-way PCV is very important in this situation.
This is designed differently and even has a two-housing connector for a vacuum.
Which controls it with electric vacuum solenoids. This can work in a lot of ways and we will go into this more in a future article.
symptoms Of A Bad Or Failing PCV Valve
#1. Check Engine Light.
One of the most common and noticeable signs of a bad PCV valve is the check engine light on the dashboard. When the light is on, there is a trouble code stored in the engine control module.
To read the trouble code from the engine control unit, you’ll have to use an OBD2 scanner. Older cars with a PCV valve fitted without an electronically controlled engine will not have this symptom.
#2. High Idle RPM/Rough Idle.
Since the PCV valve controls the airflow between the crankcase and the intake manifold, a malfunctioning PCV valve can have the same symptoms as an intake air leak.
In this case, this will cause the idle RPM to get too high then other strange idle behaviours will happen, including just 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 problems we stated above a faulty PCV valve can have the same symptoms as an intake leak. Also, the air/fuel mixture can end up being wrong. Most of the time the air/fuel mixture will go lean. If this is the case you can feel the same symptoms as from a lean mixture.
Rich mixtures very often let you see the car has a little more gray/white smoke than usual and a hint of petrol smell. Lean mixture may more difficult to make note of although it very often consists of misfires, which we will be discussing next.
#4. Misfires.
A malfunctioning PCV valve may cause lean or rich mixtures, causing your car to misfire at idle or under acceleration.
If there is a lean mixture, the cylinders won’t combust correctly, and you can get a misfire. If there is a rich mixture, you can kill the spark with the fuel and therefore misfire.
#5. Rough Acceleration.
With a bad PCV valve causing a bad fuel mixture, you can feel rough acceleration from your car, at high and low RPMs.
On most cars you won’t feel a broken PCV valve outside of idle. However, it is worth mentioning that it can happen based on the design of the valve on higher RPMs.
#6. Increased Oil Consumption & Oil Leaks.
If the PCV valve or the hoses are covered in moisture, you will create a huge buildup of pressure, which pushes pressure up into the cylinders and out of the gaskets.
If you suddenly see a dozen huge oil leaks and increased oil consumption, you should take a look at the PCV valve and your hoses to check for blockage.
#7. White/Black/Blue Smoke from the Exhaust.
If your PCV valve or the hoses are blocked, oil will push through the crankcase into the combustion chambers and the oil will start to burn inside the engine and exhaust pipe.
This will create a lot of blue smoke from the exhaust because of the oil coming out of the combustion chamber. If the PCV valve is broken AND adding a rich or lean mixture to the engine, you could have white smoke, or black based on the mixture-based issue of the engine.
In conclusion, if you see unusual smoke coming from the exhaust, make sure that your PCV valve is not broken.
Trouble Codes for PCV Valve
Here are some common trouble codes that correlate with a faulty PCV valve: If you receive one of these trouble codes from your engine control unit, you should probably check the PCV valve.
Please remember that just because you see a trouble code does not mean the PCV valve is the problem. These codes can refer to other things so I always recommend proper troubleshooting before you just start replacing 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
Where are PCV Valves Located?
The PCV Valve can commonly be Located on the valve cover, which is usually the top and it can be in a hose from the valve cover or from the air intake filter.
To find it, just follow the hose on the top of your car engine. There are some newer PCV valves that now come pre-installed with the valve cover.
PCV Valve Replacement Cost
Typically, replacing the PCV valve could cost for between $50 and $250 with variations depending on the price of the PCV Valve (typically between $20-$50) and the labor cost of the mechanic workshop ($30-$200).
If you think you know how to replace it yourself, you can save money on labor, but you may not have the time to be able to do the replacement (if under the manifold) and/or you could have trouble replacing it depending on the Scenario.
You can also find in a different scenario, you may work with a mechanic to do the work for you; at that time you appointment may be on of labor price to replace the pcv valve ($30-$200) based on your location, mechanic workshop, or type of car.
If you are working with an older car, it should not be difficult to replace the valve and, to an extent, should take a total of 10 minutes to put one in and out. On the flip side of this situation, a newer car or if the governor was located anywhere under the intake it can take over three hours to be replaced in that position.
In different situation you may have to remove the intake to even have access to the PCV valve; fortunately, this is not common.
FAQs.
Q: Can I clean the PCV valve?
If the PCV valve is clogged, yes, you can clean it. However, usually the spring mechanism becomes bad and old, and PCV valve are quite cheap. So, you can clean it, but really it would be advised to just replace it so you are not having problems close to the future.
Q: Is the PCV valve necessary?
Yes, if the PCV valve is not in place, you may have too much under pressure in the crankcase for idle, or too much over pressure during turbo boost.
Furthermore, the PCV valve improves fuel economy by recycling unburned fuel vapors back into the combustion chamber.
Q: Is a PCV valve open at idle?
The PCV valve is to be close or semi-close at idle and not create too much vacuum in the crankcase. Whenever you press the throttle a bit, the PCV valve opens wide.
Q: When do you change a PCV valve?
There isn’t any schedule upon changing the PCV valve. Usually, the PCV valve will last over 100,000 miles. Furthermore, the PCV valve is pretty cheap and easy to change, so if your vehicle is a couple of years old, you may consider changing the PCV valve.
As shown above, the majority of symptoms are engine performance concerns that could be caused by any other issue. Therefore, it is important to review the subject.
If you see any symptoms of a poor PCV valve, it’s time to take the vehicle to a mechanic to have them check your PCV valve.
It is a small part that plays a big role in having your engine work properly. So, if your PCV valve needs a replacement, don’t…wait too long until it’s taken care of. It will allow your car to run smoothly for years!