All modern vehicles have an emissions control system. You might be familiar with some components of that system, such as oxygen sensors and catalytic converters. PCV valves are also part of the system but are not as well-known.

However, despite that, if your PCV valve is failing, it could be costing you money. In this guide, we’ll explore what you need to know about your car’s PCV valve and its impact on your finances.


What Is a PCV Valve?

Long before oxygen sensors and other emissions control devices became widespread, positive crankcase ventilation was used to control emissions. This system pulls unburned gases from the oil pan and lower side of the engine and feeds them back through the air intake, ensuring that they are combusted rather than allowing them to escape into the atmosphere, where they cause air pollution.

The PCV valve is what’s responsible for sending the gases into the intake manifold via a spring-loaded plunger. The valve opens and closes as pressure builds, ensuring that the gases are recirculated without disrupting engine operation.

However, like all other components, the PCV valve is subject to wear and tear over time. Eventually, it will experience problems and will need to be replaced. Failure to do so can lead to some unwanted complications. While you’re not likely to be stranded on the side of the road, it can make driving your car uncomfortable and expensive.

What Happens as PCV Valves Age

PCV valves are subject to a lot of different forces. Mechanical wear and tear is one consideration. As the spring is compressed and decompressed, it wears and stretches. Rubber grommets will also wear over time and through exposure to caustic gases. The valve body itself, as well as the line leading to the valve, can also become clogged up with gunk, which will reduce the flow of exhaust gases through the hose and the valve itself.

Whether due to clogging or mechanical failure, a stuck or clogged PCV valve can lead to a lot of additional problems. Two of these that can cost you additional money include increased fuel consumption and increased oil consumption. The latter can also lead to engine damage if you do not check and top off your oil regularly in between oil changes.

Symptoms of a Failing or Failed PCV Valve

Not sure if your PCV valve is clogged or failing? Short of a test, there are several symptoms that you can look for. Other problems can also cause most of these symptoms, so it’s important to verify that the PCV valve is the problem. Look for more than one symptom and then test the valve to be sure.

Check Engine Light

One of the first signs that your PCV valve is bad is your check engine light (malfunction indicator lamp or MIL) turning on. Of course, there are thousands of things that could cause the light to turn on, from a loose gas cap to a failed oxygen sensor. If your check engine light comes in, it’s important to have the code checked.

Once upon a time, that meant taking the car to a mechanic shop and paying for them to read it. Today, most auto parts stores can check generic codes (proprietary codes must still be pulled by licensed mechanics with access to automaker-authorized software). There are even smartphone apps and at-home equipment that can allow you to check the trouble code yourself.

High Idle

Your car’s engine should idle relatively slow when the engine is running and the car is in park, neutral, or you’re sitting at a stop with your foot on the brake. However, if the idle is considerably higher than usual, this can be a sign that there’s a problem with the PCV valve. Note that other problems can also cause the idle to run high.

Rough Idle

Another problem that a failed or failing PCV valve can cause is rough idling. In this situation, the engine would idle low and then high, spitting and sputtering when at an idle. However, many different problems can also cause rough idling, from dirty air and fuel filters to problems with your spark plugs and oxygen sensors.

Lean/Rich Air-to-Fuel Ratio

Your PCV valve affects air intake. If it is clogged or failed, then less air will reach the engine. If it sticks in the open position, then more air than usual will reach the engine. Both can cause problems with the air/fuel mixture. You may notice that your engine is running lean – it is starved of fuel and will underperform. On the other hand, your engine may be running rich – it’s getting too much fuel. In this instance, you’ll notice white exhaust from the back of the car.

Misfires

You’ve heard it before. A car drives up the road and suddenly – BANG! – there’s a misfire. They often sound like fireworks or gunshots, and they’re caused by the problems we just talked about (running rich or lean). Misfiring is a serious problem that can lead to engine damage if it is not taken care of correctly. If you are experiencing engine misfires, have your vehicle inspected and diagnosed as soon as possible.

Rough Acceleration

When you press the accelerator pedal, you expect the engine to rev up and the car to increase in speed. It should do so relatively smoothly, as well. However, if your PCV valve is failing, you’ll likely notice rough acceleration. This includes underperformance, but it also means spitting and sputtering, stalling, and other problems, particularly at lower RPM. Note that other issues can also cause this problem, including bad oxygen sensors.

Oil Leaks

The PCV valve helps control pressure within the engine. If the valve is clogged or stuck closed, the internal pressure will rise. This puts additional wear on sensitive components, such as gaskets.

Eventually, the increase in pressure can cause gaskets to begin failing. You’ll likely notice a leak somewhere around your valve cover gasket. It will probably be slight at first but will increase in severity over time. Catching a PCV valve and replacing it as soon as possible will help you save a lot of money that would otherwise go to replacing your valve cover gasket.

Oil Consumption

As the pressure inside the engine rises, you must worry about more than just leaking gaskets. It can become severe enough that it pushes oil into the combustion chamber. When this happens, the engine will begin burning oil and you’ll notice blue-white smoke from the exhaust.

The more oil the engine burns, the less there is to lubricate the engine. Increased friction causes heat and premature wear and tear to internal engine components, eventually shortening the life of the entire engine. You’ll also deal with reduced fuel economy because of this.

Engine Sludge

The purpose of the PCV valve is to move unburned toxic gases out of the crankcase and back into the air intake, so it can be combusted. However, if the valve cannot do its job, those gases remain in the engine. In addition to increasing pressure, they merge with your engine oil, creating a thick sludge. If the sludge becomes serious enough, it can reduce fuel economy, decrease lubrication, and cause engine damage.

Reduced Fuel Economy

We’ve touched on this symptom a few times so far, but it deserves its own entry. Without a functional PCV valve, your car will see reduced fuel economy, so you’ll end up paying more than you should at the pump through more frequent fill-ups.

How Much Does It Cost to Replace a PCV Valve?

The PCV valve is one of the least expensive components on your engine and usually costs only $10 to $15. However, you will need to have it replaced, which will add to your total. A great deal depends on where you have the work done. With a branded dealership, you’re looking at around $90 to $110. However, with a local mechanic, you will likely pay between $25 and $60.

Does My Car Have a PCV Valve?

The simple answer to the question of whether your car has a PVC valve or not is “it depends.” Not all cars have a PCV valve, but all internal combustion engines must breathe, so they all have something that performs a similar function.

If your car does not have a PCV valve, then it likely has what’s called an orifice tube. Orifice tubes can be replaced, but they are simpler to clean, unlike PCV valves, which usually just need to be replaced when they begin to fail or clog up. Other cars use vacuum hoses in place of a PCV valve, and these will need to be cleaned and replaced as required over time.

To simplify it, all cars have some sort of crankcase breather system in place. That might be a PCV valve, but it might be something else. All of these systems are subject to similar issues, and while some might be easier to clean and require less frequent replacements, they still need ongoing TLC to ensure that your engine remains in good working condition, that you minimize the risk of leaks from seals and gaskets, and that you’re able to save on gas.

How Often Should I Replace My PCV Valve?

Once, PCV valves were replaced during regular tune-ups. Today, most engines don’t require tune-ups the way they once did. Chances are good that your automaker has a specific maintenance plan that dictates when PCV valves should be replaced to prevent them from failing or becoming clogged up. Most fall between 30,000 and 60,000 miles.

Note that if your engine is turbocharged, you will need to replace your PCV valve more often. You probably also have a secondary PCV system with its own valve. If both become clogged or one fails and the other is clogged, it could lead to severe engine damage.

How Do I Check My PCV Valve?

The simplest way to test your valve is to take your car to a mechanic who can usually test it in just a few minutes. However, if you have a few simple tools and some time, you can do it yourself. First, locate the valve. It will usually be on the back of the engine above the valve cover. Once you’ve located it, remove it from the hose or tube. You’ll likely need a pair of needle-nose pliers for this. Be careful not to tear the rubber hose or tube. Rubber can dry rot over time and if it tears, you’ll need to replace that as well as the valve.

With the valve free, shake it. Listen for a metallic rattling noise. If you hear a rattle, then the valve is likely still good. If you do not hear a rattling noise, then it has likely failed.

How Do I Check for a Clogged PCV Tube/Hose?

Follow the instructions above to remove the PCV valve, but remove the tube/hose, as well. Check to see if there is gunk within it or if there is visible oil leaking out of it. The tube should be dry and free of any debris/blockage. The good news is that you should be able to clean any gunk out of the tube/hose and then reinstall it.

In Conclusion

Your car’s PVC system plays an important role in controlling emissions and improving fuel economy. If the valve sticks open or closed, or the tube/hose is clogged up, you will experience a wide range of symptoms, including rough idling, spitting and sputtering, decreased fuel economy, and even oil leaks or burning oil.

If you notice any of these symptoms, or your check engine light is on, it’s important to have the situation diagnosed by an experienced mechanic. While the problem could well be the PVC valve, many other issues have similar symptoms and an experienced mechanic will be able to determine the actual underlying cause and repair the problem.

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