The PCV valve is responsible for redirecting blowby gases to the engine where they’re burned during normal operation.
If the PCV valve fails, you might notice the following symptoms: excessive oil consumption, rough idling/stalling, oil leaks, sludge, and an illuminated check engine light.
It’s not advisable to drive with a bad PCV valve because it can cause the gaskets to blow.
What Is A PCV Valve?
“PCV” stands for “positive crankcase ventilation.” A PCV valve is integral to the positive crankcase ventilation system (PCV) system. It is also known as the crankcase ventilation system.
Your vehicle’s crankcase holds your engine’s motor oil and is located at the bottom of your vehicle’s engine. The PCV valve is a one-way valve attached to the crankcase of your car’s engine and removes unwanted gases from the crankcase. It produces gases when your engine burns fuel.
A crankcase is an intrinsic component of an internal combustion engine and works mainly to store and circulate oil in the crankshaft.
These gases result from blow-by that occurs when fuel, oil, and exhaust vapors slip by the piston rings. All internal combustion engines produce blow-by gases.
Key Takeaway:
- The PCV valve is responsible for redirecting blowby gases to the engine where they’re burned during normal operation.
- If the PCV valve fails, you might notice the following symptoms: excessive oil consumption, rough idling/stalling, oil leaks, sludge, and an illuminated check engine light.
- It’s not advisable to drive with a bad PCV valve because it can cause the gaskets to blow.
What does a PCV valve do?
In short, the PCV valve redirects unwanted and harmful gases away from the engine. When your vehicle’s engine combusts fuel and air inside its cylinders, gases are formed. These are a mixture of unburnt fuel and exhaust, and are known as ‘blow-by’ gases. This is because they ‘blow by’ the piston rings into the crankcase on the downstroke of the pistons.
The valve, which is attached to the crankcase, works to stop any stray engine gases from remaining in the crankcase where they would mix with the oil and form a sludge, which can clog your car’s engine. It also works to relieve pressure in the crankcase, which otherwise would cause oil leaks and damage your engine’s seals.
Where is PCV valve located?
The PCV valve location differs from vehicle to vehicle, but it’s generally attached to the valve cover near the air intake. If you’re looking at the crankcase, the valve is attached to a rubber tube that connects to the intake manifold.
Bad PCV Valve Symptoms
If your PCV valve is malfunctioning, you will notice several distinctive symptoms. Here are just some of the symptoms that you might notice:
- Discolored exhaust gas that is white, black, or blue
- A check engine light warning
- Rough idling and acceleration
- Whistling or hissing noises from the engine
- Increased fuel consumption
- Misfiring
- Engine oil leaks
#1. Discolored exhaust gas that is white, black, or blue.
If the positive crankcase ventilation valve is stuck open, you may notice blue smoke from the exhaust pipe. That’s because a stuck valve forces excess engine oil vapors to mix with fuel and crankcase gasses during combustion.
This causes the engine to burn the air-fuel mixture along with engine oil. Hence, the exhaust pipe releases blue smoke. Sometimes, the exhaust gas emission can also appear white or black instead of blue.
#2. Illuminated Check Engine Light.
A clogged PCV valve can cause the Engine Control Unit (ECU) to trigger the Check Engine Light and produce a DTC code.
Some common trouble codes often associated with a faulty PCV valve include:
- 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
#3. Rough Idle/Stalling
The PCV valve pulls air and gases through the crankcase and into the engine. If the valve is stuck open, the extra air entering the engine will disrupt the air-fuel mixture, causing problems, such as rough idle and stalling.
#4. Whistling Or Hissing Noises 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.
#5. Increased Fuel Consumption.
Suppose your car’s PCV valve is stuck open or closed. In that case, it can throw off the air-fuel mixture ratio in the combustion chamber, leading to irregular engine operation, a drop in fuel efficiency, and increased engine emissions.
#6. Misfiring while Idling
Another common bad PCV valve symptom is misfiring with the engine. 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.
#7. Engine oil leaks
When the PCV valve is stuck closed, the blow-by gasses and oil vapor accumulate, resulting in excessive crankcase pressure buildup. This could lead to oil seeping out of the PCV system seals and valve cover.
So, if you see puddles of oil underneath the car and there isn’t any damage to the oil system, you can safely assume that the oil leak stems from the PCV system or valve cover. If the oil leak is left unattended, you could have fouled spark plugs and excessive oil consumption.
Note: The excessive crankcase pressure from a faulty PCV valve can create a strong suction on the oil cap or leave a film-like residue on its underside. If your PCV valve is clogged, harmful gasses can accumulate in the crankcase oil, leading to sludge formation inside the engine.
How To Test A PCV Valve?
Checking your PCV valve is an easy task that can be completed at home and once out of the car, you can run a few tests to know for certain if this is the root of your vehicle issues. After removing and cleaning the valve, shake it and listen for clicking sounds from the metal plunger inside. If you don’t hear anything, the plunger is either missing or stuck and needs to be replaced.
You can also remove the PCV valve from the valve cover with the hose still attached and place your finger over the open end. If you feel a strong suction, the valve is working correctly. If the suction is weak or non-existent, an obstruction is present in the valve.
If you’ve discovered your PCV valve is in need of replacement, don’t worry. The fix is simple and can be completed by a professional or even by you at home!