Can a PCV Valve Cause Misfire? (Quick Answers)

The full form of PCV is Positive Crankcase ventilation. PCV valve is situated at the crankcase of the engine. It is responsible for reducing emissions done by the crankcase. The PCV valve sends the toxic gases produced by the crankcase back into the combustion chamber. 

Today, we are going to find out whether a PCV valve can cause a misfire.

Can a PCV valve cause misfire?

A PCV valve that has gone bad can certainly cause a misfire in the car engine. A bad PCV valve alters the air-fuel mixture of the engine and causes misfires. A bad PCV valve reduces the overall performance of the car and whistling noises can be heard from the engine when a PCV valve goes bad.

Let’s look at different states of the PCV valves and see if they can cause a misfire in the engine of the car.

Bad PCV valve:

Positive Crankcase Ventilation (PCV) valve is one of the most important components of the engine. It controls the emissions done by the crankcase and keeps the engine healthy and the environment clean. A PCV valve can have disastrous effects on the car engine.

A PCV valve does not have a definite functioning period. You have to regularly check your PCV system to find out if the PCV valve has gone bad. Blown-out seals and gaskets are a good indicator of a PCV valve going bad. 

You will also find sludge inside and around the engine if your PCV valve has gone bad.

A bad PCV valve will also cause the check engine light to come on. You will also hear noises sounding like whistles coming from the engine if your PCV valve becomes faulty. A bad PCV valve will fail to control the airflow into the engine. 

The mismatched mixture of fuel and air in the engine would cause the engine to misfire.

A PCV valve can become bad if the PCV vacuum hose has a hole in it. The leak would cause excessive airflow into the engine. If the excessive airflow continues, the engine will start misfiring.

Clogged PCV valve:

PCV valves can sometimes become clogged and fail to do their functions properly. A clogged PCV valve will cause oil leaks inside the engine. It will increase the fuel consumption of the engine.

A PCV valve’s main job is to send emissions produced by the crankcase back into the combustion chamber through the intake manifold. If a PCV valve becomes clogged, it will build up pressure in the crankcase because of the excessive gas. 

This event can cause possible misfires in the car engine.

Does the PCV valve cause engine misfire when at low rpm?

The full form of rpm is revolutions per minute. It is usually used to find out the rotational speed of something around a fixed axis. Usually, low rpm is the aftereffect of a bad PCV valve. Engine misfire is a mixture of many things.

First of all, a bad PCV valve will alter the air-fuel mixture of the engine and as a result, it will cause the engine to rough idle. It can further cause a misfire in the engine. Cars are designed to run at low rpm. But the rpm can fall even lower because of rough idling. 

So low rpm is an aftereffect of the bad PCV valve and not the cause of it.

Is the PCV valve leak causing misfire?

A PCV can cause engine misfire in several ways. First of all, if the PCV valve hose has a leak in it, it will change the proportion of the air-fuel mixture in the engine. It will then cause misfires in the engine. But a PCV leak is not the only cause behind the misfire in the engine. 

The PCV valve stuck open or shut can also misfire in the engine.

You will need to find out the leak in the PCV valve and repair it immediately. Otherwise, the performance of your engine will drop down and affect the health of your car. The check engine light coming can indicate a leak in the PCV valve. 

You will also hear loud noises coming from the engine when the PCV valve develops a leak.

When does the PCV valve cause a misfire?

The PCV valve causing a misfire depends on a lot of factors. First of all, if your PCV valve has reached the sixty thousand miles limit. 

Generally, a PCV valve stays good for this mileage period if it is serviced on a regular basis. An out-of-date and old PCV valve will cause a misfire in the engine.

If any part of the PCV valve develops a leak, that is when it will cause a misfire in the engine. When the PCV valve gets clogged up, it will cause a misfire in the engine. 

A stuck open or a stuck shut PCV valve can also cause the engine to misfire by altering the air-fuel mixture of the engine.

What are the signs of a bad PCV valve? What happens when a PCV valve goes bad?

If your PCV valve goes bad, it will start showing several signs. Let’s discuss in detail about them and see what happens when a PCV valve goes bad.

An increase in oil consumption:

A bad PCV valve will increase the oil consumption of your car. A bad PCV valve will fail to send back gases produced in the crankcase into the combustion chamber. This will increase the pressure in the crankcase. 

As a result, the crankcase will start leaking oil with the help of gaskets and seals.

If you notice drops of oil under your car, then it can mean that the crankcase has started leaking oil because of your PCV valve going bad. It is a clear sign that you should replace or repair your PCV valve.

A decrease in mileage:

If your PCV valve becomes bad, then it will decrease the mileage of your car. The overall performance of the engine will also decrease because of a bad PCV valve.

Pollution in breather element:

The breather element filter of the car will become polluted if your PCV valve goes bad. The excessive pressure of the crankcase will leak water vapor into the breather element. The water vapor then gets mixed with the gas and pollutes the breather element.

Extra noises from the engine:

A bad PCV valve will cause the engine to make extra noises. If you hear noises sounding like whistles coming from the engine, you can be sure that the PCV valve has gone bad.

The check engine light coming on:

A bad PCV valve will cause the check engine light to come on. When this happens, you will need to check the PCV valve immediately.

Misfires in the engine:

You can have a lean or rich mixture because of a bad PCV valve. This lean or rich mixture will cause the engine cylinders to misfire.

Can you fix the PCV valve? How to fix the PCV valve that causes misfire?

If your PCV valve starts failing or becomes worse, you can certainly fix the valve. This process involves several steps. Let’s discuss them in detail.

Check the hoses:

First of all, you will have to check the parts of the PCV valve to find out where the problem lies. You will have to start by inspecting the PCV valve hoses. A PCV valve normally has two hoses. They are known as inlet hose and outlet hose. 

You will have to look for cracks on the hoses. If the hoses have cracks, then you will have to replace them with new ones.

Check the grommets and seals:

You will have to look for cracks on the rubber grommets and seals of the PCV valve. If there is a crack on them, you will have to replace the rubber grommets and seals. The crack on rubber grommets and seals is the reason behind the PCV valve going bad.

Check the mesh filter:

You will need to check the mesh filter as well. If the mesh filter is faulty, you will need to replace it as well.

Check the entire valve:

Sometimes valve can become so bad that fixing or replacing parts of it will not solve the problem. In that case, you will need to replace the entire valve. The valve can be easily removed from the rubber grommets. 

A wrench can always come in handy in situations like this.

Attach the new valve:

You will then have to attach a new PCV valve to the rubber grommets and seals. After that, you can start the engine in order to inspect the new valve for any leak.

Final Thoughts

A faulty and bad PCV valve has the ability to cause misfires in the car engine. A bad PCV valve decreases the performance of the engine. It also fails to send toxic gases back into the combustion chamber. The environment gets affected because of a bad PCV valve along with the car.