The PCV valve is responsible for transferring excess air-fuel mixture from the crankshaft to the intake manifold to be used by the engine.
Over time of use, the PCV valve can get damaged, causing more fuel consumption and a high emission rate.
Like any other mechanical component in your vehicle, your PCV valve would tell you when its getting damaged before it even does.
In this article, we provide you with an overview of the PCV valve and what does it do. Then, we highlight the main signs of a bad PCV valve for you to keep an eye for. If you’ve experienced any of these signs, you must get your vehicle inspected by a professional mechanic to avoid high repair costs. Finally, we provide a rough estimate of how much to expect to replace your vehicle’s PCV valve.
What is the PCV valve, and what does it do?
The Positive Crankcase Ventilation system (PCV) is the oldest emissions system mandated by law for all United States’ automobiles. Within this system, the PCV valve is responsible for transferring excess fuel-air mixture from the crankshaft to the intake manifold. Without this valve, the crankshaft might get damaged as the excess fuel mixture builds up.
All PCV valves are usually designed in the same way or the same design idea. Each valve consists of two hoses connected to a one-way spring-loaded valve.
The way the PCV valve works differ when your engine is idling versus when it is at revving. When you drive at higher RPMs or rev your engine, the PCV valve opens and allows the access pressure to escape your vehicle’s crankcase. On the other hand, when you are idling or running your vehicle at lower RPMs, the crankcase will have lots of vacuum and no need for the PCV valve to release any pressure.
As your PCV gets older or clog, it might not be able to do the job, and lots of pressure might go back to the combustion system resulting in either damaging the crankcase or blowing the head gasket.
Signs of a bad PCV valve
Now you understand what the PCV is and what it does, it is important to keep an eye for signs of a bad PCV valve. In this section, we provide the list of the most common signs
Drop-in fuel economy
While poor fuel economy can be due to many reasons, a bad PCV valve might be the culprit.
When the PCV valve is clogged or damaged, the intake manifold will not receive the required amount of fuel. The intake will request additional fuel supply to the combustion system, thinking there is insufficient fuel. Consequently, your vehicle will consume much more fuel than usual, and you will have frequent visits to the gas station.
No matter what the reason is, if you experienced a significant drop in fuel economy, you must get your vehicle inspected and repaired by a professional mechanic as soon as possible to avoid high repair costs.
Rick or lean air-fuel mixture
In any combustion engine, the is a specific air-fuel-ratio the engine must receive for the best performance. If there is more fuel in the mixture than air, the mixture is called “rich.” On the other hand, if there is more air than fuel in the mixture, the mixture is called “lean.”
Both lean and rich mixtures are not good for your engine and will cause significant problems and affect the overall performance of your vehicle.
When the PCV valve gets clogged, the engine will not receive the right amount of air and fuel; thus, it will either run lean or rich. As a result, you will notice a significant change in your engine’s performance.
Check engine light illuminating
Your vehicle’s internal computer uses different warning lights to indicate internal problems. Some of these errors might be due to simple problems; others can be due to significant issues.
While check engine light illuminating can be due to many reasons, a bad PCV valve might be the culprit.
To confirm that it's your PCV valve causing the problem, you can use an OBD2 reader and translate the error code from your vehicle’s computer.
For instance, a P052E error code indicates a general issue with the PCV valve performance.
Either way, whether it's your PCV valve or something else, if your check engine light illuminates, you must take quick action and get your vehicle inspected and repaired by a professional mechanic as soon as possible.
With a bad PCV valve, the engine might not work properly and start shaking, “engine misfire,” or vibrating, especially when idling. It is not surprising to have an engine misfire with a bad PCV valve; if the valve is clogged or broken, the engine will not receive the required amount of air-fuel mixture to one of its cylinders, causing engine misfire.
Weird noises coming from the engine
In general, if you hear any strange noise coming from any part of your vehicle, you must take your vehicle to a professional mechanic; the problem can be very complicated and might result in significant issues with your vehicle.
When dealing with a bad PCV valve, your engine will make hissing sounds due to a leak in the PCV valve hose. Consequently, your engine might experience a misfire, run rough, and get into more complicated problems.
Black or white smoke coming from the tailpipe
When the PCV valve or hoses are clogged, the crankcase will push the excess oil back to the combustion system resulting in black smoke coming out of the vehicle’s tail top due to oil burning.
While a faulty PCV valve might cause weird smokes coming out of the exhaust system, there are other causes for the same symptom, like issues with the fuel injector or other engine components.
No matter what the reason was, if you see weird smoke coming from the exhaust system, you must take your vehicle to a professional mechanic and get it diagnosed and repaired.
Engine accelerating roughly
Rough acceleration at lower and higher RPM can happen because for several reasons. One of these reasons can be issues with the PCV valve. When the problem is related to the PCV valve, you will notice the rough acceleration at lower RPM versus higher RPM.
Excessive oil consumption
Like many other mentioned signs, excessive oil consumption happens due to problems with several engine components.
When you drive a vehicle with a clogged or damaged PCV valve or hoses, you might notice a significant increase in oil consumption, which is not surprising. When the PCV hoses are clogged, the crankcase will not have anywhere to send the excess pressure. Instead, it will send the pressure back to the chambers resulting in an oil leak from the other side. As a result, you will notice that the engine’s oil is dropping every time you check it.
Oil reduction is not a good thing when it comes to the engine’s safety. In severe cases, excessive oil consumption can cause complete engine damage.
As your vehicle’s PCV valve gets older, the crankcase might not handle the excessive pressure build-up. As a result, the crankcase sends water vapor to the filters causing oil gas mixture once the oil and gas get mixed, resulting in filter contaminating.
How much does it cost to replace the PCV valve?
Luckily, replacing the PCV valve is one of the cheapest mechanical repairs for your vehicle. For the PCV part itself, expect to pay around $10 only. However, the labor cost can build up and increase the total bill significantly depending on the place you get the job done.
For instance, if you decided to get the repair done at a dealership, the repair cost can get much higher than replacing it at a small mechanic shop.
Many people who have the required mechanical skill take it to the next level and replace their PCV valve on their own using available DIYs.
How often should I replace my PCV valve?
While there is no specific interval for how often you should replace your PCV valve, it is not rare to deal with a bad PCV valve as its made of plastic that can be affected by extreme temperatures around the combustion system.
Thus, when you notice any of the mentioned signs of a bad PCV valve, do not wait or ignore the problem and have your vehicle inspected by a professional mechanic to confirm there are no other issues with your vehicle.
How to clean a PCV valve?
Cleaning the PCV valve is a good habit to avoid dealing with complicated problems and to prevent the need for PCV valve replacement.
To do so, you need to follow the following steps:
- If your engine has the plastic cover on, you need to unbolt the large bolts on the sides and remove the cover.
- Once the engine cover is removed, you can easily find the PCV valve, usually a red valve connected by a hose to the middle top part of your engine.
- Remove the hose clamp and pull the hose away from the PCV valve
- The PCV valve is usually held in place by a rubber grommet that needs replacement if it gets very old.
- Once the hoses and the grommet are out, you can pop out the PCV valve
- Before cleaning the PCV valve, ensure that there is no rattling or clicking is indicating a damaged PCV valve.
- Since the PCV valve is a very simple part, there is no risk of damaging it using any strong type of cleaner.
- For instance, you can use a carburetor or brake cleaner to clean the PCV valve
- For better cleaning, you can spray a WD-40 to make the ball move perfectly
- To confirm that the valve is completely cleaned, try to shake it and listen for a rattling sound showing that the ball is moving smoothly
- Once you hear that, you are good to go and place the PCV valve right on the correct place
Can a bad PCV valve cause overheat?
It is very unlikely for a bad PCV valve to cause engine overheating. The PCV valve only affects the engine’s mixture and making it either lean or rich.
Engine overheating usually happens due to problems with other components like issues with the thermostat, coolant, water pump, and other components of the cooling system.
Is it worth replacing the PCV valve?
Well, as we mentioned earlier, replacing the PCV valve is one of the cheapest repairs you can do. However, if your vehicle has multiple other complicated problems requiring repair costs close to the worth of your vehicle, it might not be worth the time replacing the PCV valve.
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Your vehicle’s PCV valve is part of the emission system that allows access to the air-fuel mixture to leaves the crankcase to prevent damaging the combustion system.
Over time of use, the PCV valve can get clogged or completely damaged. If this happened, you must get it replaced as soon as possible to avoid dealing with complicated issues that require high repair costs. What’s even better is detecting issues with the PCV valve before it gets completely damaged.
Luckily, certain unique symptoms are indicating a bad PCV valve. Some of these symptoms are drop in fuel economy, engine misfire, excessive oil consumption, black or white smoke out of the vehicle’s tail top, and others.
If you noticed any of the mentioned problems, you must get your vehicle inspected by a professional mechanic as soon as possible.