Bad PCV Valve Symptoms & How To Fix

The PCV valve handles the rerouting of blowby gases to the engine to be used as fuel during regular functioning.

When the PCV valve malfunctions, you might observe the following symptoms: high oil consumption, rough idle or stalling, leaking oil, accumulating sludge, and a check engine light switched on.

Driving with a broken PCV valve is not recommended because it may lead to gaskets blowing.

What Is A PCV Valve?

“PCV” stands for “positive crankcase ventilation.” A PCV valve is vital to the positive crankcase ventilation system (PCV). It is also referred to as the crankcase ventilation system.

The crankcase in your vehicle serves to store the motor oil, which is located at the lower section of the engine. A PCV valve is a one-way valve stationed at the crankcase of your vehicle’s engine, Its primary task is to vent the crankcase gases from the engine.

Your vehicle’s engine produces gases whilst burning fuel, resulting in gas chamber production.

A crankcase is an essential part of an internal combustion engine. It serves the purpose of oil storage and circulation, specifically in the crankshaft.

Every type of engine produces what is referred to as “blow-by” gases, which are a result of fuel, oil, and exhaust vapors bypassing the piston rings.

What does a PCV valve do?

In short, the PCV valve takes care of moving hazardous exhaust gases. The combustion of fuel and air within the pistons in your vehicle’s engine leads to the generation of ‘blow-by’ gases, a combination of unburnt fuel and exhaust.

The valve attached to the crankcase serves to block any wayward engine gases from escaping the crankcase, as it would combine with oil and form sludge, which would be detrimental to your car’s engine.

It also relieves pressure in the crankcase that would otherwise lead to oil leaks and damage the seals of your engine.

Where is the PCV valve located?

The location of the PCV valve differs from one vehicle to another, but it is usually found mounted on the valve cover close to the air intake. While observing the crankcase, the valve is affixed to a flexible hose that leads to the intake manifold.

Bad PCV Valve Symptoms

There are some symptoms you may notice if your PCV valve is damaged. Here are a few of the most noticeable symptoms:

#1. Check Engine Light.

The engine control unit (ECU) uses many sensors to keep track of how well your engine is running, including an oxygen (O2) sensor, which monitors the fuel-to-air mixture in the engine.

In case of a failing PCV valve, it will disrupt the somewhat delicate balance of air and fuel in the system by letting in either too much air or fuel into the combustion chambers, which lights up the check engine alarm on your dashboard.

When scanning your vehicle, you may find specific related codes like P052E or P053A. However, the more common codes you will find are P0171 or P0174, which show a lean condition where the PCV valve might be one of numerous potential causes. Always make sure to scan for trouble codes to correctly identify the issue.

#2. Rough Idle and Engine Stalling.

When your PCV valve fails to close, it permits an excessive quantity of air to flow into the combustion chambers. This causes what mechanics refer to as a “lean condition,” wherein there is too much air versus fuel in the mixture.

Due to this, your engine may idle roughly, with noticeable vibration or irregular RPMs while stationary at a stoplight. In the worst-case scenarios, the engine may completely stall while idling or coming to a stop.

The issue becomes particularly evident when your engine is already warm; you may observe an unusual RPM fluctuation at idle. If left unattended, this problem can escalate over time.

#3. Increased Oil Consumption.

If you notice yourself adding oil more frequently than usual between designated oil change windows, you may have a faulty PCV valve. A malfunctioning PCV system may generate an unusually high vacuum in the crankcase, which can pull oil into places that should not be accessed.

Oil is usually combusted within the combustion chambers or sucked into the intake system, and in many cases, there are no external leaks but rather sneaky burns taking place.

More likely is when you notice that you need to add a quart or more of oil between scheduled oil changes when you previously had not done so. The lack of excessive oil consumption, in addition to being expensive, can lead to carbon accumulation on valves and other internal components of the engine.

If you notice that this is a problem, more frequent checks of oil levels are recommended.

#4. Oil Leaks.

A properly working PCV valve prevents the condition of having too much or too little oil in the engine’s crankcase.

When the valve fails, particularly when it gets stuck in the closed position, pressure builds up inside the engine. This excess pressure often forces oil past gaskets and seals that would normally contain it.

Under normal operating conditions, you could see oil spots under your vehicle or oil build-up around valve covers, oil pan gaskets, or main seals. In some cases, oil can enter the intake manifold, throttle body, or air filter housing.

These leaks not only lead to an untidy engine bay but, if not attended to quickly, can cause low oil levels and likely engine damage.

#5. Poor Fuel Economy.

Keeping your PCV valve closed will lead to an excessive combination of fuel and air in your combustion cylinders, meaning it is mostly fuel-based.

This increases the amount of fuel being consumed, lowers your fuel economy, which results in paying more money for gas. In addition to that, your vehicle’s engine will increase the number of toxic gases it emits, which increases the chances of failing an emissions test.

When a valve sticks in the closed position, too much fuel enters the combustion chambers to the air, leading to what is known as a “rich” fuel condition. Your Engine’s PCV helps adjust for this imbalance, and instead of spending fuel properly, the outcome will usually result in higher fuel consumption.

If you have noticed the need to make frequent trips to the gas station, this indicates the amount of fuel being consumed is significantly high, meaning the MPG is considerably low. This condition not only impacts the finances significantly, it also has the potential to damage the spark plugs, catalytic converter, and catalytic converter.

So, you are getting ready for the upcoming state emissions test? Well, the previously mentioned condition will guarantee you fail, and having a failing hydrocarbon emission means that swapping the PCV valve is the solution.

#6. White or Bluish Exhaust Smoke.

Strange, bluish white exhaust smoke on cold starts or during hard acceleration indicates that there is an issue with the combustion chambers of the engine. It is a tell-tale sign of PCV valve problems and is an indication of oil being burnt in the combustion chambers.

Some people make the mistake of believing this phenomenon is the result of normal condensation on a cold morning. However, unlike condensation, this remains even after the engine is warm, albeit in lesser quantities.

#7. Engine Sludge.

A malfunctioning PCV valve will allow exhaust gases to escape into areas where they combine with oil. The result is thick and sticky sludge, which is a dark gel-like exterior. It coats various components within the engine and can block oil passageways.

During oil changes, the previously mentioned sludge is going to be the place where the thick, dark, and tar-like oil is located.

Along with the thick oil causing the new sludge, one of the symptoms of this problem is a clicking noise coming from the valve. The reason for this is that the valve is not getting properly lubricate. If you are concerned about the possibility of this slow turning problem, you should start with more frequent oil changes.

#8. Rough Acceleration.

When you press down on the gas pedal, your vehicle’s engine should respond predictably and escalate in a linear manner. On the contrary, if the PCV valve is bad, you may experience acceleration issues, including hesitating, stumbling, or inconsistent power delivery.

In the case of a defective valve, it is equally problematic in a dead zone where fuel isn’t injected—float zones that result in blends that are too rich or lean. For your vehicle, you may notice the issue most when you try to accelerate from a complete stop or attempt to merge onto a motorway.

This makes it appear akin to the engine is “holding back,” or surging in an erratic manner rather than delivering smooth propulsion as one would expect. It’s more likely to become noticeable when the PCV valve issue gets progressed as the temperatures go up, it is not usual PCV weather, and tend to show up more on sun-soaked days.

#9. Whistling or Hissing Noises.

When attempting to pinpoint a problem, distinctive sounds are usually helpful clues. In a case of a failing PCV valve, you may notice a whistling, hissing, or with a little luck some fluttering sound coming from the bay of the engine.

The sound usually becomes the most obvious when the hood is open as you add some revs to the engine. Moreover, noise itself changes pitch or intensity when the engine is revved. The reason behind these sounds is that the valve’s plunger or spring mechanism isn’t operating correctly and air is allowed to pass in ways that aren’t intended.

While various issues can cause engine noises, a protruding sound alongside other symptoms from this list typically is indicative of PCV valve problems.

PCV Valve Replacement Cost

The national average PCV valve replacement cost—including labor and parts—generally falls between $186 and $220.

Part Cost: Depending on the make and model of the vehicle, the price of the PCV valve ranges from $2 to $15, making it relatively affordable.

Labor Cost: Although the labor cost for the work may differ, it typically isn’t particularly complicated, therefore, most of the expense goes to labor.

When to Replace a PCV Valve

Certain models deem the PCV valve a scheduled service part, thus requiring a periodic replacement based on the maintenance timetable. Others, like those where the valve is housed within the valve cover, are replaced only when an issue arises.

If your valve is already exposed, it is likely to be replaced between 20,000 to 50,000 miles of driving.

However, the more common reasons to get a PCV valve replacement include the following:

• A stuck PCV valve leads to increased oil use. The closed valve can cause oil to get forced past the piston rings to burn in the cylinders.
• Spark plug failure or misfiring. When oil is allowed access to the combustion chamber, it causes the plugs to get drenched in oil, making them incapable of ignition.
• Decreased fuel economy. This happens because the engine is not working properly, which causes it to adjust the fuel-air mix that is used.
• Running Problems. Your vehicle may run rough during idle or at low RPM.
  Oil Drips. Excessive crankcase pressure may cause an oil seal to unseat or tear, resulting in a significant oil leak.

How To Test A PCV Valve?

It is simple to check your PCV valve and does not require the help of a mechanic. After you remove the valve and clean it, there are a couple of tests you can conduct that will tell you if your valve is the reason why the car problems are occurring.

The first test is shaking the valve and listening for clicks. The absence of sound suggests that the plunger is lodged or entirely missing, and in such a case, replacement is necessary.

There is the option of taking the PCV valve along with the attached hose out from the valve cover and covering the hole with your finger. If there is a decent amount of both power and suction felt, the valve is functioning correctly.

In cases where there is weak or no suction at all, there is some blockage in the valve, and therefore it will not function correctly.

In the case that you need to replace the PCV valve, there is no need to worry,y as you can simply get it professionally done or do it yourself at home, as the process is quite straightforward.