{"id":3762,"date":"2020-05-21T10:00:22","date_gmt":"2020-05-21T17:00:22","guid":{"rendered":"https:\/\/www.emanualonline.com\/blog\/?p=3762"},"modified":"2025-04-10T08:34:58","modified_gmt":"2025-04-10T13:34:58","slug":"bad-pcv-valve-most-common-symptoms-and-fixes","status":"publish","type":"post","link":"https:\/\/www.emanualonline.com\/blog\/bad-pcv-valve-most-common-symptoms-and-fixes","title":{"rendered":"Bad PCV Valve: Most Common Symptoms And Fixes"},"content":{"rendered":"

Modern internal combustion engines are true engineering marvels. It’s very likely that in the future, we will look down at them as one of the most ingenious inventions of humankind. Despite the fact that internal combustion engines had humble beginnings, today, it\u2019s one of the most complex pieces of equipment that we use every single day.<\/p>\n

Apart from transforming heat into mechanical energy, modern engines have many secondary systems that take care of various things. These systems and parts weren\u2019t initially used in ICEs; however, their introduction made motors more reliable, durable, and efficient.<\/p>\n

A great example of that is the PCV valve. At first glance, this is just a small component that many people think their vehicle can work without. And it absolutely can. Not that we recommend doing it, though. An engine without a PCV valve will quickly lose performance and efficiency. Oh, and that is just a few of the potential issues \u2013 other bad PCV valve symptoms are even more dangerous.<\/p>\n

If you want to keep your car in perfect working condition, regularly inspecting the PCV valve and replacing it when required is essential. Luckily, replacing a PCV valve is not only easy, but it\u2019s also cheap, especially if you do it yourself. You can even replace it as a precautionary measure and give your engine a little breathing room.<\/p>\n

To give you a better understanding of the PCV valve, I\u2019ll cover everything there is to know about this component. Apart from its role, I\u2019ll point out all potential bad PCV valve issues and how they affect your driving. Moreover, if you want to take your game to the next level, I\u2019ll indicate how you can replace it yourself.<\/p>\n

\"PCV<\/p>\n

What is the Purpose of the \u201cPositive Crankcase Ventilation\u201d Valve?<\/h2>\n

For starters, PCV stands for \u201cPositive Crankcase Ventilation,\u201d and the PCV valve is part of the EVAP system<\/a>. I know it\u2019s hard to relate to this part only by its name. I had the same issue the first time I encountered bad PCV valve symptoms in my own car. Don\u2019t worry, though \u2013 the PCV valve is a pretty simple part. What it does is significant, though \u2013 that\u2019s why we even bother dedicating a whole article to it.<\/p>\n

To better explain the purpose of the PCV valve, we need to start with the basics. And by basics, I mean burning fuel inside the combustion chamber. When an engine runs, every combustion creates gasses, which are then thrown out via the exhaust system. I suppose you already know that.<\/p>\n

Now, the pistons inside a car engine have rings that should keep the same gases from entering the crankcase. And, while they mostly succeed in doing that, a tiny amount of waste gasses will still pass through. More often than not, the fumes will contain unburned fuel. This can create all sorts of problems, which we will discuss further down below.<\/p>\n

The \u201cPositive Crankcase Ventilation\u201d valve is designed to recapture the gasses using the engine\u2019s vacuum. Or, as its name suggests, it ventilates the crankcase from the exhaust gasses that slipped past the piston rings. Dead simple, isn\u2019t it?<\/p>\n

Then, using a small hose, the PCV valve redirects the gasses into the intake manifold. By doing so, the engine can burn all the unburned fuel from previous strokes. This improves overall efficiency as most of the fuel is used to power the engine instead of being thrown out unused.<\/p>\n

Also, unburned fuel is much worse to the environment than burned one, so the PCV valve helps with emissions, too.<\/p>\n

How Does A PCV Valve Work?<\/h2>\n

There are two PCV systems \u2013 open and closed. The former uses a vented oil filler cap to draw fresh air from the environment. This system was only used on older vehicles and can\u2019t deal with larger amounts of gasses. In the case of excessive gasses in the crankcase, it will force them through the cap and into the atmosphere. Recent environmental regulations simply don’t allow that anymore.<\/p>\n

Closed systems, on the other hand, draw air through the filter housing and channel the crankcase gasses back to the intake manifold. Closed systems won\u2019t let gasses escape into the atmosphere. Because of that, this system is very effective at limiting air pollution. For this reason, closed PCV systems are widely used in modern vehicles.<\/p>\n

The PCV valve itself is very simple in its operation. The main purpose of the valve is to control the flow of vapors from the crankcase to the intake manifold. Usually, at lower engine speeds, the PCV valve stays closed due to a lower amount of gasses in the crankcase. At higher engine speeds, the PCV valve opens so it can quickly lower the pressure inside the crankcase.<\/p>\n

To do all of these things, the PCV valve uses the vacuum from the intake manifold. When the vacuum is higher (lower engine revolutions), the valve is only slightly opened. When the vacuum is lower, for example, when the gas pedal is suddenly depressed, the valve opens up.<\/p>\n

\"PCV<\/p>\n

Most Common Symptoms of a Bad PCV Valve<\/h2>\n

A bad PCV valve can cause many serious issues, especially if not taken care of on time. Here are the most common bad PCV valve symptoms:<\/p>\n