Bad PCV Valve Symptoms and How to Test the PCV Valve Yourself

What’s a PCV valve?

PCV valve means constructive crankcase air flow. It’s designed in a one-way format, often hooked up to the valve cowl, consumption manifold, or engine block, relying on the engine design. Nonetheless, 90% of PCV valves are discovered on a rubber grommet on the engine valve cowl. The aim of the PCV valve is to remove emissions from the crankcase and export them to the consumption manifold. When the emission will get to the consumption manifold, the consumption manifold sends them again to the engine for an additional combustion cycle to repeat, making the engine emission cleaner and more practical.

What Occurs When a PCV Valve Fails?

Signs of a Caught Closed PCV Valve or System

A nasty PCV valve or associated element can produce a variety of signs. For instance, if the valve clogs, or will get caught within the closed place, you'll discover certainly one of these signs.

  • Improve in inside engine strain
  • Failure of a number of oil seals or gaskets
  • Engine oil leaks
  • Low whistling or moaning noise
  • Moisture and sludge buildup contained in the engine
  • Engine surges
  • MAF sensor hassle code
  • P0171 or P0174 hassle codes
  • 02 sensor hassle codes

Signs of a Caught Open PCV Valve

If the PCV valve will get caught open, or a system hose will get disconnected or ruptured—producing a vacuum leak—you'll discover a number of of those signs.

  • Engine misfires at idle
  • Lean air-fuel combination
  • Presence of engine oil in PCV valve or hose
  • Elevated oil consumption
  • Exhausting engine begin
  • Tough engine idle
  • Presumably black smoke
  • Oil fouled spark plugs

A PCV valve caught open can set off the "verify engine" mild on account of elevated airflow. A diagnostic laptop might erroneously blame this mild on a mass airflow sensor or oxygen sensor as a substitute, making it tougher so that you can detect the actual supply of the issue.


PCV Valve Substitute Value

The typical PCV valve substitute value is between $50 and $250, relying on the automotive mannequin and labor prices. A PCV Valve principally prices between $20 and $50. The labor value is between $30 and $200 at a mechanic workshop.

The substitute value of defective PCV valves can differ considerably relying on the engine and the automotive you’ve. Nonetheless, the PCV valve’s value is usually meager, and you may anticipate costs of round $20-50 for a model new valve.

If you happen to suppose you’ve the information to switch the valve your self, you’ll not endure from the labor prices, however do not forget that it may be tough to switch it if it’s situated below the manifold on some vehicles.

If you’d like a mechanic to switch it for you, you’ll be able to anticipate a labor value of $30-200, relying on the placement and the automotive kind.

Total, when you’ve got an older automotive, the PCV valves are sometimes simple to switch and will solely take round 10 minutes, whereas on newer vehicles, there could possibly be a substitute time of over 3 hours if it’s situated below the consumption. Generally, it’s important to take away the consumption to entry the PCV valve; fortunately, this isn’t that widespread.

Unhealthy PCV Valve Signs

To make sure that your car emits the cleanest and lowest emissions doable, it should have a correctly working PCV valve. Sadly, PCV valves may fail after a few years of utilization.

You need to establish dangerous PCV valve signs in your automotive if you wish to substitute it. The vast majority of such indications are fairly simple to identify.

Merely be cautious to not overlook these indicators, as they could end in irreparable hurt to your engine. The next are probably the most prevalent indications of a malfunctioning PCV valve.

Poor Gasoline Economic system

As soon as your PCV valve turns into jammed closed, your gas effectivity might endure. This happens since your PCV valve permits sure air into your engine whereas it’s open, which might be considered by your engine management unit (ECU).

This assists the pc (ECU) in adjusting the air and gas combination adequately. Nonetheless, together with your PCV valve jammed closed, inadequate air will attain the engine, ensuing within the operating wealthy of your engine.

This reduces gas effectivity and raises the extent of emissions produced by your engine.

Contaminated Filter

In case your PCV valve fails, a filter referred to as a breather factor may get polluted with oil and hydrocarbons.

That is attributable to rising crankcase strain that forces water vapor via your breather factor. Water combines with the fuel, inflicting a buildup and maybe rising your automotive’s gas effectivity.

A bodily inspection of this filter for accumulation is one method to guage this element. One other technique is to find out your car’s gas financial system. If it begins to drop abruptly, your PCV valve could possibly be failing.

Tough Idle/Elevated Idle RPM

Since your PCV valve regulates airflow throughout your consumption manifold and crankcase, a broken PCV valve may exhibit the identical signs because the consumption air leak.

Leading to extreme idle RPM and varied peculiar idling patterns equivalent to a extremely rough idle. If you happen to’re experiencing uncommon idling points, it’s often prudent to examine your PCV valve first.

Lean/Wealthy Combination

Because of the difficulties outlined, a malfunctioning PCV valve may current with related indications just like the consumption leak, leading to an incorrect air/gas combination.

Usually, the air/gas combination turns into lean, and also you’ll expertise the exact same indicators related to a lean combination. Because of a rich mixture, you’ll often discover that your car produces considerably extra white or grey smoke than traditional, in addition to a powerful scent of petrol.

Though a lean mixture is more difficult to find out, it incessantly leads to misfires.

Unusual Engine Noises

If both your PCV valve or valve hose fails, your engine might start to make uncommon sounds. You may hear a whirring or whistling noise coming from behind your hood.

This noise is created by air escaping out of your valve or its valve hose’s gap. Preserve an ear out for noises or different surprising engine noises since an irregular noise practically often signifies one thing is wrong.

Engine Misfires

Since a malfunctioning PCV valve may end in a posh lean/wealthy combination, you could possibly discover misfires throughout idle and acceleration if the PCV valve is broken.

When the combination is excessively lean, your cylinders received’t ignite correctly, leading to misfires. The gas might successfully extinguish the spark each time the combination is excessively wealthy, leading to a misfire.

Tough Acceleration

After you have a malfunctioning PCV valve leading to an incorrect gas combination, you’ll discover that your car accelerates poorly at decrease and better RPMs.

Whereas most cars is not going to really feel a broken PCV valve above idle, it’s value noting since it’d happen primarily based in your valve’s configuration.

Engine Oil leaks

As you’re in all probability conscious, the PCV valve permits fuel to flee from the engine crankcase. As soon as your PCV valve fails to perform appropriately, fuel accumulates throughout the crankcase, rising its inside strain.

When the strain throughout the crankcase reaches a sure degree, it may push engine oil out by way of the a number of gaskets and seals.

Take be aware once you discover some oil puddling beneath your car. And in that case, study your engine and its crankcase for any oil leaking out from behind the seals. This could be a sign of a clogged PCV valve.

Black/ White/ Bluish Exhaust Smoke

In case your PCV valve turns into jammed shut, the strain inside your crankcase may naturally rise. Oil may seep out from the seals on account of this, nevertheless it may additionally be pushed up in the direction of your combustion chambers.

When this occurs, the engine oil will start to burn, altering the colour of your exhaust. To be extra exact, the exhaust fuel can be a lot smoky than typical and will have a bluish hue.

Blue exhaust fumes are by far the clearest indicator that your engine is consuming oil, and you should by no means overlook it when you detect it.

Engine Stalling

Every time your PCV valve fails, its plunger might stay open. An abnormally giant quantity of air will enter the combustion cylinders when this happens.

This leads to a lean air/gas combination since there’s extra air contained in the cylinders than gas. As a consequence, your engine may stall or idle poorly.

Examine Engine Gentle

Your dashboard’s check engine light is arguably probably the most prevalent and obvious indicator of all malfunctioning PCV valve issues. Your engine management unit shops a fault code each time your engine mild comes on.

To learn your engine management unit’s fault code, you should make the most of an OBD2 scanner. Sure older autos geared up with a PCV valve however not geared up with an electronically regulated engine received’t exhibit this signal.

The way to Check Your PCV Valve

If you’re experiencing any of the issues outlined above, then there’s a probability that your PCV valve has failed or is caught open. The issue, as we’ve got described, is that you could be not get exact readings out of your diagnostic laptop as to the reason for the issue. If not one of the points highlighted by your engine verify system is the issue, then you have to verify the PCV valve. There isn’t any one PCV valve take a look at; nonetheless, there are just a few steps you’ll be able to take to find out whether or not it’s working appropriately.

To do that, you have to first establish the PCV valve and the hoses related to it. Start your checks by inspecting the rubber components of the valve. If these are worn, then the half must be changed. Subsequent, establish the mesh filter beneath the valve and substitute it. If this doesn’t remedy your downside, then disconnect the hoses and scrutinize them. Cope with any points you discover right here or substitute the hoses if wanted earlier than reconnecting and checking if the issue is solved. One remaining take a look at is to take away the valve itself and provides it a shake. If the PCV valve doesn’t rattle, then it must be changed.

3. Total poor efficiency

Because the PCV valve begins going dangerous, the efficiency of your car will worsen. This may be exhibited by a buildup of strain within the exhaust or the engine may stall out. The dangerous PCV valve might not shut all the best way, so oxygen might get into the combustion chamber. When this occurs, the gas and air combination is diluted inflicting your car to run poorly and lean out.

If you happen to discover your car is leaking oil, consuming giant quantities of oil, you’ve a contaminated filter, or the automotive will not be working prefer it ought to, have the PCV valve checked out and changed. It will hold your car operating easily and hold your gas financial system the place it needs to be. YourMechanic makes getting repairs to your positive crankcase ventilation valve simple by coming to your location to diagnose or repair points. YourMechanic’s skilled technicians are additionally accessible for any questions which will come up. You may guide a service on-line 24/7.


PCV system points could be tougher to establish if they aren’t associated to the valve. Carry it to your trusted mechanic to look at it over once you suspect an issue elsewhere however are not sure what it’s.

If it will get to that time, you may require extra skilled help. If the difficulty is simply your PCV valve solely, you’ll don’t have any issues resolving it by yourself. It’s in all probability of the only duties you’ll be able to accomplish by automotive measures.

Keeping track of the state of your PCV valve ensures that your engine operates at peak effectivity, preserving you safe and sparing you cash. Confirm that your understanding of the indicators of a malfunctioning PCV valve is up to date to make sure which you can have it repaired asap.

We hope that this text was informative and can help you in diagnosing the issue together with your car.


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Changing a PCV Valve

The PCV valve can have issues, however greater than doubtless, the PCV valve filter is the perpetrator. Filters are extremely essential elements of your automotive. You’re doubtless aware of the oil filter and air filter. The PCV valve filter is an important a part of the PCV valve, because it captures many of the toxins within the fuel stream. Over time and pure put on, the filter can change into clogged with highway particles and dirt.

It’s endorsed that the PCV valve filter get replaced each 60,000 miles. Common servicing will embody a verify of this filter, so your trusted BMW mechanic will warn you in the event that they really feel it’s crucial to switch this earlier than that mileage mark.

Widespread Bother Codes Related to the PCV Valve

Some widespread hassle codes seem with a defective PCV valve. If you happen to expertise any of those hassle codes from your engine control unit, it’s in all probability time to verify the PCV valve.

Do not forget that simply since you see these hassle codes, it’s not 100% that the PCV valve is damaged. These codes may also be different issues, and I at all times advocate you perform correct troubleshooting earlier than changing any components.

  • P052E – Optimistic Crankcase Air flow Regulator Valve Efficiency
  • P0171 – Gasoline System Too Lean (Financial institution 1)
  • P0300 – Random/A number of Cylinder Misfire Detected
  • P053A Optimistic Crankcase Air flow Heater Management Circuit /Open

The PCV Valve Can Develop into Caught

It’s doable that the PCV valve can change into caught, failing to do its job to scale back dangerous vapors from circulating within the engine. Nonetheless, there may be one other sensor that mimics the identical issues. That is the MAF sensor. It has related signs as a caught PCV valve. The MAF sensor is simpler to restore. Inform your mechanic in case you be aware any of the next, which may level to an malfunctioning MAF sensor:

  • your engine misfires whereas idling
  • operating lean or wealthy
  • elevated oil consumption price
  • troubles with ignition
  • tough idling

When to Change Your PCV Valve

In concept, the PCV valve ought to final roughly indefinitely, and can solely need to be replaced if it actually breaks. Nonetheless, it’s doable to revive a gunked-up valve to its unique situation by cleansing it.

Dirty Vs Clean PCV Valve
Soiled Vs Clear PCV Valve

Cleansing the valve is definitely fairly simple;

  • Simply get your self some carburetor cleaner, pour a few of it right into a container, and let the valve soak in it for some time.
  • The valve will be thought of clear as soon as it’s freed from gunky deposits and if the valve’s colour seems even. 

If this doesn’t work, you’ll must swap out your previous valve for a brand new one, however fortunately that is additionally fairly simple. All you have to do is take away the previous valve from the valve cowl and disconnect it from its hose, set up the brand new valve, and reconnect the hose.

Can I Nonetheless Drive With a Unhealthy PCV Valve?

Technically you’ll be able to, as a foul PCV valve doesn’t current any speedy issues of safety, however we’d strongly advocate towards it nonetheless. Whilst you as the driving force received’t be in any speedy hazard from a foul PCV valve, your engine actually will probably be. Driving for too lengthy with a busted valve could cause all kinds of mechanical issues.

In case your valve has certainly stopped working, it is best to have it mounted as quickly as you’ll be able to, except you wish to run the chance of getting to repair considerably dearer failures sooner or later. 


You can even verify the PCV for the vacuum when you acknowledge the signs of a foul PCV valve. Let the engine heat up for about twenty minutes to verify with the vacuum. Entry the hood and disconnect the valve from the valve cowl. Once you block the tip of the valve together with your finger, it appears like sucking your fingertip. You’ll discover a pace drop of about 40 to 80 rpm.

When the RPM is greater than that, the valve could be caught open. Once you really feel no suction impact, verify the valve and hose for any obstruction and clear it. You can even clear the valve and hose with lacquer thinner and a skinny hose brush, and you’re finished.