Many automobiles have breather systems that include a PCV (positive crankcase ventilation) valve, particularly those that include a pipe connecting the breather to the inlet manifold.
When your car’s PCV valve goes faulty or the hoses that feed the system get clogged, you’ll experience different warning signs The major one is the reduction in engine performance.
Fortunately, the PCV valve is neither expensive nor difficult to test, clean, and replace. Changing or servicing this component won’t cost you much.
Well, in this reading, we’ll explore what a PCV valve is, its functions, and a diagram. We’ll also explore the symptoms of a bad PCV Valve
What is a PCV Valve?
Many cars have a PCV (positive crankcase ventilation) valve installed as part of the breather system, particularly those with a pipe connecting the breather to the inlet manifold.
This helps draw any blow-by gases out of the crankcase and recycle them through the inlet at low engine speeds, preventing oily deposits from being dumped on the road.
Your car’s pressure and airflow are regulated by the positive crankcase ventilation valve, or PCV valve. While it is a part that is frequently forgotten during regular service, your car will run differently if the PCV valve is not working fine.
However, in the event of a backfire, the one-way PCV valve closes to protect the breather system from the high temperatures of a backfire.
The PCV is also used in turbocharged engines, where a pressurised inlet manifold (under boost conditions) would mean blowing boost directly into the crankcase if a one-way valve were not installed.
Related: Engine Knocking: Its Causes and What it Sound Like
Diagram
Signs of a Bad PCV Valve
You’ll also not notice the following signs of a bad PCV valve: engine noises, check engine light, misfiring while idling, oil spills, high fuel efficiency, black exhaust smoke, and rough acceleration.
1. Engine Noises
While driving, strange noises are a sure sign that something isn’t working properly. A hissing, whistling, or whining sound coming from the engine, and occasionally a deep moaning murmur, is one of the most typical signs of a faulty PCV valve.
A leak in the PVC hose is most likely to be blamed for the hissing sound.
2. Check Engine Light
A faulty PCV valve is one of the possible causes of the Check Engine Light appearing on your dashboard because it works directly with your engine.
Keep in mind that if you drive an older model car, the PCV system may not have been installed if your engine was electronically controlled; as a result, a faulty PCV valve won’t turn on your check engine light.
The engine control unit (ECU) stores a fault code that activates when the engine light appears. You’ll need an OBD-II scanner or code reader to read the engine control unit’s fault code to determine the precise issue with your PCV system.
3. Misfiring While Idling
A misfire will sound like the engine is vibrating, which is a surefire symptom that the engine is not running at its best. Typically, when a situation like this arises, the car is idling.
Vacuum leaks, particularly one-cylinder-confined ones that let more air into the affected cylinder and disrupt the ideal air and fuel mixture, are the cause of engine misfiring.
4. Rough Idle
A faulty or broken PCV valve might present itself in the same way as an intake air leak because it regulates the flow of blow-by gases from the crankcase to the intake manifold.
A defective PCV valve can result in excessive idle RPMs and odd idle behaviours, such as extremely rough idling.
5. Oil Spills
The pressure inside the engine crankcase will rise if the PCV valve or the hoses are blocked, and since there is no other route for the pressure to be released, the oil in the cylinders will be forced out through the seals and gaskets.
Inspect the PCV valve and the hoses going to the valve to make sure they aren’t blocked if you suddenly discover many sizable oil puddles passing into the floor of your garage (upon inspection, oil is leaking through the seals).
6. Poor Fuel Efficiency
The correct air and fuel ratio mixture, which is necessary for ideal combustion, will be thrown off by a broken PCV valve.
This is because the vacuum on the cylinder head’s intake side will be unable to accurately estimate how much fuel should be injected into the cylinder for combustion.
7. Black Exhaust Smoke
The increased crankcase pressure will force engine oil into the combustion chambers, where it will be burnt and escape through the exhaust pipe if the PCV valve or the hoses connecting to it are blocked. Your tailpipe will emit a lot of blue smoke if you are burning oil.
8. Rough Acceleration
When the air and fuel mixture provided to the engine is thrown off by a faulty PCV valve, you may experience jerky acceleration at both high and low RPMs.
On most cars, this scenario will be less noticeable at higher RPMs than it is at idle, but depending on the PCV valve’s design, it may still occur.
Conclusion
Sustaining engine performance and pollution control depends on being aware of the signs of a failing Closed PCV (Positive Crankcase Ventilation) valve.
To avoid potential issues and guarantee the effective operation of the vehicle’s emission system, it is important to pay close attention to these symptoms as soon as they appear.
Related: What Is An Engine Lubrication System? Its Functions And Parts
FAQs
What happens when the PCV valve is bad?
You will experience engine performance issues.
A bad PCV valve can affect the air-to-fuel ratio, potentially causing rough idling, poor acceleration, or reduced fuel efficiency. Emissions Problems: A defective PCV valve can lead to increased emissions, which might cause your vehicle to fail emissions tests.
What does the PCV valve do?
A PCV valve’s main job is to control emissions and reroute any gas the crankcase produces into your engine’s combustion chambers. Doing so can safely burn these gases without harming your vehicle or the environment.
How do I know when my PCV valve needs replacing?
If you can feel the suction and the idling drops slightly, the airflow is normal, the blockage has been cleared and the valve is operating as it should. However, if you can’t feel the vacuum or there’s a dramatic drop in engine revs, the PCV valve is overdue for replacement.
Can a PCV valve cause oil burning?
PCV valves cause engines to burn oil by raising the internal pressure to levels that the gaskets and seals can’t handle, and it pushes oil out through them. While not technically “burning,” this still causes cars/engines to lose oil over time, but only when running.
Can PCV cause fuel consumption?
Your car’s PVC system plays an important role in controlling emissions and improving fuel economy. If the valve sticks open or closed, or the tube/hose is clogged up, you will experience a wide range of symptoms, including rough idling, spitting and sputtering, decreased fuel economy, and even oil leaks or burning oil.
