Symptoms of a Bad PCV Valve

If you’ve been driving for a while, chances are you’ve heard of a PCV valve that’s located inside your engine, but you’ve probably never learned what it’s for and how it helps your engine. In many engines, the PCV valve is an important component but it can cause a lot of problems for your engine and this problem happens in almost all engines.

PCV valves are plastic and they contain a metal spring inside them. Since the PCV valve is small and plastic, after driving for many years, it can wear out. Due to the hot environment that it’s contained in, it is going to wear out over time and because of its importance, you’ll notice a lot of this going wrong within your car. When the PCV valve, there are symptoms your car will give you, so you know if you’ll need to replace it.

What is a PCV Valve

A PCV valve is a Positive Crankcase Ventilation and it’s an emission device that’s used in a lot of vehicles. The PCV valve removes crankcase emissions from the crankcase and sends them the intake manifold where its combusted again in another engine cycle. This allows your engine to clear out emissions more effectively. All PCV valve across all vehicles are made similarly and contain two connectors with a spring-loaded valve inside it.

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When your engine is idle, there’s a lot of vacuum in the intake manifold and this helps to suck out the emissions from the crankcase efficiently when you’re driving at lower speeds. When you’re driving at higher speeds, and the RPMs are higher, the PCV valve will open even more in an attempt to suck out even more emissions from the crankcase ventilation which is caused by more pressure building up within the crankcase. When your RPMs are low and the engines idle, the vacuum is higher and the PCV valve is half-closed. If your RPMs are higher, then the vacuum is low but the PCV valve is fully open. If there’s backfire from the crankcase, then the PCV valve is closing.

If you have a turbocharged engine, boosting the pressure up to go into the crankcase can cause the oil to leak and a blown gasket. The crankcase is the housing for the crankshaft in the engine. The crankcase shields the crankshaft and protects the connecting rods from debris. If you do have turbo engines that allow you to boost pressure to the crankcase, its important that the PCV valve is one way. These PCV valves are different and it only works on idle and low RPMs. This means that a lot of vacuum is used.

Check Engine Light

The most common way to know that there’s a problem with your PCV valve is if the check engine light comes on. If there is a problem with the valve, the check engine light will start to illuminate. When the check engine light gets triggered on, it’s because the engine control unit isn’t able to regulate or maintain a problem within the engine’s systems. When the check engine light comes on, you’ll need to check why using an OBD2 scanner tool. A professional OBD2 scanner tool will allow you to look up the error code on the scanner, whilst a standard OBD2 scanner tool will force you to look up the error codes meaning in your car’s manual.

There are several error codes that the scanner will return once it’s scanned. You’ll need to look for one that’s linked to the PCV valve. If the scanner told you the error code and the error codes mean there something wrong with your PCV valve, you’ll need to get it replaced. If you have an older car with a PCV valve that’s fitted without an electronically controlled engine, then the check engine light won’t come on. If you don’t have an OBD2 scanner, the problem with using the check engine light as a symptom is because the check engine light can come on for a list of different reasons. It only comes on when there’s a problem when the EGU can regulate or maintain a problem and sometimes emissions from the crankcase can’t be removed.

High Idle RPM

Since the PCV valve controls the airflow and the intake manifold that provides the right air-fuel mixture, a faulty PCV valve can have the same symptoms as an intake air leak. This can cause the idle RPM to get high. If your RPMs are high when the car is idle, chances are that your PCV valve is broken. Another symptom that can show you the PCV valve is damaged is if your car behaves strangely when idle. In general, if your car isn’t the same as it usually is when idle, you’ll need to get it replaced.

Lean or Rich Fuel-Air Mixture

Because the PCV valve controls the airflow that goes inside the intake manifold, a faulty PCV valve can lead to the wrong air-fuel mixture. A faulty PCV valve also provides the same symptoms as an intake air leave because the right amount of air isn’t being mixed with the right amount of fuel. In most cases, there won’t be enough air that gets to the intake manifold; therefore, the air-fuel mixture will turn on wrong. With the wrong air-fuel mixture, a hold host of problems can manifest within your car.

Misfire

When the engine misfires, it means that one of the cylinders inside the engine failed to fire correctly. This can be caused by the wrong air-fuel mixture being combusted in the combustion chamber. If the PCV valve is faulty, the incorrect amount of air will be provided to the intake manifold which can result in the cylinder combusting the wrong air mixture. When this happens, it can cause the cylinders to fail when they’re firing, and this is an engine misfire. If the PCV valve isn’t replaced immediately and your engine continues to misfire, this can lead to long term damage to your engine.

Vibrating

If your car starts to vibrate, this can be an indicator that your PCV valve is broken. If the incorrect air from the intake manifold is provided to the cylinders and they don’t fire correctly, this can cause your engine to become unbalanced and this can cause vibrations inside the bonnet whether you’re idle or accelerating. If you notice your car shaking, it can also be a symptom of other issues and not just a bad PCV valve.

Rough Idle

If the incorrect air-fuel mixture is made by the intake manifold due to a faulty PCV valve, this can cause your idle to be uneven and you may feel the car jump up and down due to a misfire. The misfire can also cause the car to turn off when idle.

Loss of Power

If you’ve noticed that your engine’s power has gone down and your car is now driving with less horsepower and RPM, then this could indicate that your PCV valve is broken. A broken PCV valve can provide the wrong amount of air and this will lead to the intake manifold creating the wrong air-fuel mixture. If the engine receives this, this can result in your car using less power. It can also put your car in limp mode, and this can stop your vehicle from revving past 3500 Rpms.

Smoke Coming from Exhaust

If the PCV valve is broken or blocked and it can’t remove the emissions from the crankcase, the crankcase will push the oil into the combustion chambers and this can cause the oil to burn inside the engine and exist through the exhaust pipe. The smoke can end up coming out in different colors such as whist and blue. If the PCV valve is faulty and providing the intake manifold with the wrong amount of air, this will lead to a rich or lean air-fuel mixture. Depending on the mixture the engine’s been provided, white, blue or black smoke could be coming out of the exhaust.

Rough Acceleration

Since the PCV valve can provide the intake manifold with the wrong air which can lead to the wrong mixture in the engine, you may feel a rough acceleration when on high or low RPMs. On most cars, you’ll feel a broken PCV valve on lower RPMs and are less likely to feel them on higher RPMs. This all depends on what’s wrong with the PCV valve and the design of it.

Increased Oil Consumption

If the PCV valve is blocked, this can cause the crankcase to build up pressure and this pressure can be pushed into the cylinders out from the gasket. If you see large oil leaks or a larger oil consumption in your car, you should check the PCV valve and hoses for any blockages.

How to Fix the PCV Valve

If there’s a problem with the PCV valve, it’s going to cause the emissions to remain in the crankcase and this means that the engine won’t be able to combustion problems. Failing to maintain components in your vehicle such as the PCV valve can blow the engine and this costs a lot to rebuild. You need to make sure that you’re maintaining your vehicle’s components often to make sure it doesn’t have a knock-on effect and damage other components.

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More Symptoms

Engine Changes Sound

If the PCV valve is faulty and the wrong air-fuel mixture is being provided to the engine, after driving your car for a while, you may notice that it has a certain sound and that sound stays pretty consistent whilst driving. If you notice that your engine sounds different, then this could be a symptom that your engine is misbehaving due to the wrong mixture. If you’re using a 4-cylinder engine and you notice that the engine sounds like a 3-cylinder engine, one of the cylinders could have may have misfiring incorrectly causing it to sound like that.

Smell

If the PCV valve is broken or blocked, the crankcase will push the oil into the combustion chambers, and this can cause the oil to burn inside the engine and exist through the exhaust pipe. If you notice that there’s a smell coming from your exhaust, this could indicate that your PCV valve is broken. You’ll notice the smell coming out of your exhaust pipe and can be strong enough to fill up your car. Since the PCV valve controls the air that goes to the intake manifold, if it’s wrong, this can lead to more fuel being burned off which can cause a pungent smell to come out of the exhaust.

Decreased in Fuel Economy

If you’ve noticed that your fuel economy has decreased, this can be caused by the wrong air-fuel mixture in the engine. If your engine has started to misfire because of the broken PCV valve giving the wrong amount of air to the intake manifold, the other cylinders that didn’t misfire have to work harder to compensate for that one cylinder that did misfire. This can cause a decrease in fuel economy and increase your emissions.

Engine Overheating

If you can feel that the engine is getting excessively hot, then this can be an indicator that the PCV valve is faulty. This can be caused by the incorrect air-to-fuel mixture provided by the intake manifold due to a faulty PCV valve. An engine that continues to overheat can lead to the long-term damage of your engine and the complete shutdown of your car.

Can You Continue to Drive with a Faulty PCV Valve?

If the PCV valve is broken and provides the wrong amount of air to the engine via the intake manifold, the air-fuel mixture exits the engine and goes to the exhaust system. Since all cars that drive on the road require a catalytic converter, the mixture will go to the catalytic convert so it can get rid of the toxic gases – this helps to reduce your car’s emissions. When the catalytic converter is getting rid of toxic gasses, it can reach temperatures of 600F and when unburnt air-fuel gets into the catalytic converter, it can explode inside the catalytic converter.

If you continue driving whilst you’re your PCV valve is faulty, this can damage your catalytic converter and you’ll need to replace it. If you also notice that your engine keeps misfiring due to this, you’ll need to get it checked out immediately because this can lead to long term damage to your engine and repairing/replacing this is expensive.