Want to extend the life of your engine and improve its performance? Paying attention to your PCV valve is key. A healthy PCV valve means a healthier engine. Learn to recognize the bad PCV valve symptoms to keep your car running at its best.
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What Does A PCV Valve Do?
Before we dive into bad PCV valve symptoms, you must understand how PCV valves work.
One major role of the PCV valve has to do with emissions. It is one of the oldest and most used emission devices in automobiles.
The PCV valve function is to transfer emissions from the crankcase through the PCV valve hose to the intake manifold, where the excess gas can be used as fuel. Therefore, these gases are combusted again in another engine cycle instead of being wasted.
The second major role of the PCV valve is to deal with moisture inside the engine, which is harmful to all engine parts. When the engine runs, it generates heat, which creates condensation as the engine cools down.
When condensation forms, it results in excess moisture. Usually, additives present in engine oil will absorb this excess moisture and hold it in suspension. Over time though, as condensation increases, engine oil additives can no longer absorb excess moisture.
When this occurs, moisture will attack the metal parts of the engine, causing corrosion and further damage, which can result in malfunction.
The PCV valve gets rid of engine condensation by using a manifold vacuum that draws those harmful vapors to the intake manifold. These vapors then get mixed with the fuel-air mixture to burn in the combustion chamber.
What are The Symptoms of a Bad PCV Valve?
A failing PCV valve can manifest in several ways. Here are some common symptoms to watch out for:
Noise from the engine
When you hear a strange sound while driving, it is a telltale sign that something is not working properly. One of the most common bad PCV valve symptoms is a hissing or whistling or whining noise from the engine, and sometimes a low moaning sound. The hissing sound is most probably because of a leak in the hose of PVC.
The easiest way to verify whether a bad PCV valve is indeed the culprit is to temporarily block the vacuum source to the PCV valve.
If the noise changes or goes away, you should immediately take your car to an auto repair shop, as ignoring it can cause misfires, rough running, vacuum leaks, and all kinds of performance problems you wouldn’t want.
Check engine light warning
There may be various reasons for the Check Engine Light illuminating on your dashboard, and a bad PCV valve is one of them, since the PCV valve works directly with your engine.
Do note that if you own an old model car, the PCV system might be fitted without an electronically controlled engine, and thus a bad PCV valve will not cause the Check Engine Light to illuminate.
When the engine light shows up, there is a trouble code stored in the engine control unit (ECU). To read the trouble code from the engine control unit to find out exactly what is wrong with your PCV system, you will need to use an OBD-II scanner or code reader.
Some common trouble codes often associated with a faulty PCV valve are as follows:
- P052E – Positive Crankcase Ventilation Regulator Valve Performance
- P053A Positive Crankcase Ventilation Heater Control Circuit /Open
- P0171 – Fuel System Too Lean
- P0300 – Random/Multiple Cylinder Misfire Detected
If you get any of these trouble codes from your ECU, you should have your PCV valve inspected by a professional, or do it yourself by following the steps provided further below.
But note that just because you get the above codes doesn’t guarantee that a bad PCV valve is indeed the culprit for your issues. These codes can also be triggered by problems elsewhere.
Therefore, after the code reading, do not proceed to replace the PCV valve right away but pay attention to other unusual symptoms and carry out proper troubleshooting to better pinpoint the reason.
Misfiring while idling
Misfiring with the engine is also one of the most common positive crankcase ventilation failure symptoms. A misfire will sound like the engine has a vibration to it, and it is a sure sign that the engine is not in optimal operation.
This kind of situation usually happens when the vehicle is idle in most cases. The reason behind engine misfiring is vacuum leaks, especially those that are confined to one cylinder, which allows more air to reach the affected cylinder and throw off the optimal air and fuel mixture.
Engine misfiring also happens when there is a loss of vacuum due to a blockage in the PCV hose due to buildups of sludge, fuel and oil varnish deposits over time, or if the hose is pinched.
Rough Idle
Because the PCV valve controls the flow of blow-by vapors from the crankcase to the intake manifold, a faulty or broken PCV valve can manifest itself in the same way as an intake air leak. A bad PCV valve can cause the idle RPM to get too high and unusual idle behaviors like very rough idling.
Oil Leaks
If the PCV valve or the hoses are clogged, the pressure inside the engine crankcase will get very high, which will push the oil in the cylinders out through the seals and gaskets since there’s no other way for the pressure to be released.
If you suddenly see several large oil puddles dripping onto the floor of your garage (upon inspection, oil is leaking through the seals), and if you notice increased oil consumption, inspect the PCV valve and the hoses to the valve to make sure they’re not blocked.
Engine running lean/Rich & poor fuel economy
Another common sign of a bad PCV valve is poor fuel economy. A malfunctioning PCV valve will throw off the ratio of the air and fuel mixture, which needs to be precise for optimal combustion.
This is because the vacuum on the intake side of the cylinder head will not be able to properly determine the correct amount of fuel to be supplied to the cylinder for combustion.
Another reason is a bad PCV valve that might be stuck open or may not close all the way can let oxygen get into the combustion chamber.
As a result, the fuel can be lean or rich. When the correct amount of fuel is not delivered for optimal combustion, this means poor fuel economy.
Smoke from exhaust
If the PCV valve or the hoses to it are blocked, the high pressure in the crankcase will push engine oil into the combustion chambers, where the oil will be burned and go out through the exhaust pipe. Burning oil will cause a lot of blue smoke from your tailpipe.
Otherwise, you can get thick white or black smoke coming out from the exhaust pipe in the case that a bad PCV valve is causing a rich or lean mixture, depending on what type of mixture problem the engine has.
Rough acceleration
When you have a bad PCV valve that’s throwing off the air and fuel mixture fed to the engine, you might notice rough acceleration on high and low RPMs. On most cars, you will less likely notice this scenario on higher RPMs than during idle, but it can still happen depending on the PCV valve’s design.
How to Test Your PCV Valve
If you’re experiencing one or more of the above bad PCV valve symptoms, it’s time to inspect the component and see what could be causing it to malfunction.
Inspect PCV valve grommets
In most cases, a pliable rubber grommet is inserted into a hole in the valve cover to seal the PCV valve to the cover and secure it in place.
Sometimes, the valve may screw in or twist in and seal with an O-ring. No matter what the design, the PCV valve must always be sealed nicely and tight to the engine, which means that any leak is problematic.
Due to the nature of their material, rubber grommets and O-ring seals harden over time and crack or split, thus causing an oil leak and allowing contaminants to enter the engine.
This is why whenever you replace the PCV valve, you must swap in a new rubber grommet or O-rings as well as a preventive measure. Note that grommets come in a variety of designs, depending on the engine design, so make sure you get the right one.
Inspect PCV valve hoses
PCV inlet and outlet hoses are also prone to natural deterioration. Over time, they will harden and can crack or split.
PCV system’s hoses are designed to be oil resistant, but do also check if the hoses are oil soaked and swell up, which would impede their ability to seal properly. A leaking PCV inlet or outlet hose can allow contaminants to enter the engine and can cause a Check Engine Light.
Always replace PCV hoses with the original equipment molded hose from your vehicle manufacturer. Swapping in the wrong PCV hose types will most surely cause oil leaks and sludge buildups, as well as other PCV system failures.
Check for moisture contamination
While you’re inspecting the PCV valve itself, check for moisture contamination in the form of a cloudy or milky film in the PCV valve or hose. If there is moisture in the system, you’ll need to replace the valve.
That said, moisture in the PCV valve is an indication of other problems, and replacing the valve alone won’t fix the problem, but you also need to change the oil. Otherwise, the problem remains and symptoms will soon return.
In general, if you mostly drive your vehicle on short trips, particularly under ten miles, moisture buildup is more serious, which means you will need more frequent oil changes.
Together with the oil changes, try to combine your errands so that every time you turn the key, you’re driving for longer cycles. But even after that, if the moisture buildup problem is not lessened, then some other engine problems are causing moisture contamination.
How To Replace a PCV Valve
Replacing the PCV valve is very straightforward, and locating/ accessing it is also easy. Most PCV valves simply push into a rubber grommet. Just remove the exit hose and make a slight twist to break them free. Pull lightly to remove the valve.
Some valves use a quarter-turn system, which must be rotated a quarter turn, counter-clockwise to remove. A few other designs are threaded in and must be unscrewed to pull out. Note that to lower costs, some automakers have adopted a restrictor to substitute for the PCV valve.
FAQs About PCV Valve
Is it safe to drive with a bad PCV valve?
It’s generally not recommended to drive with a bad PCV valve for extended periods. While it might not be immediately dangerous, it can lead to increased emissions, reduced fuel economy, and potential engine damage.
How much does it cost to replace a PCV valve?
The average PCV valve replacement cost is between $80 and $250, depending on your vehicle’s make and model, and varying labor costs between states. This range does not include taxes and fees, as well as related repairs that come up during the inspection.
How often should the PCV valve be replaced?
Ideally, the PCV valve should be changed with every major scheduled service, that is at 30,000 miles, 60,000 miles, 90,000 miles, and so on, according to what your vehicle manufacturer recommends. Neglecting your scheduled servicing and regular oil changes will shorten the lifespan of your PCV valve.
Can I clean a PCV valve instead of replacing it?
In some cases, you might be able to clean a PCV valve with a carburetor cleaner. However, if it’s severely clogged or damaged, it’s best to replace it.
Endnote
A healthy PCV valve is essential for a healthy engine. By recognizing the warning signs of oil leaks, strange noise, or misfiring…, you can prevent more serious problems down the road and keep your car running smoothly for years to come.
