How To Diagnose A PCV Valve Failure In Your BMW

Your BMW’s PCV valve is responsible for controlling emissions from the crankcase. PCV is an acronym for Positive Crankcase Ventilation. The PCV valve removes crankcase emissions and transfers them to the intake. They also further undergo combustion in another engine cycle for more effective and cleaner emissions.

A bad or faulty PCV valve may affect the performance of your BMW. It could result in pressure buildup within your BMW’s exhaust, affecting your engine’s overall performance. A bad PCV valve can also result in a less concentrated fuel/air mixture, thereby reducing your vehicle’s overall performance.

Therefore, knowing when your PCV valve is faulty is crucial to the smooth running of your vehicle. Let’s find out how to diagnose a bad PCV valve.

Warning Signs of a Malfunctioning PCV Valve!

Illuminated check engine light

One of the most noticeable and common signs of a faulty PCV is a check engine light glowing on your BMW’s dashboard. Although the check engine light could have resulted from other factors, including a bad oxygen sensor, failing spark plugs, or faulty catalytic converter, it could also be due to a failing PCV valve.

Rough Idle

Another effective way to diagnose a bad PCV valve is when you notice a very high or idle RPM. Your BMW’s PCV valve helps control airflow between the intake manifold and the crankcase. An intake leak may cause strange idle behavior, including a rough or very high idle. When you notice this, you should take your BMW to a specialist to have the PCV checked.

Rich or lean fuel mixture

An intake leak may show similar symptoms as a faulty BMW PCV valve. When your PCV valve is bad, it may cause an irregular fuel/air mixture, thus forming a lean mixture. A lean mixture may be difficult to diagnose. However, it may cause your BMW to misfire. Misfires may occur due to an irregular lean/rich mixture associated with a faulty PCV valve in your BMW.

When you have a rich mixture, you may notice more white or gray smoke from your exhaust system. You may also perceive the smell of fuel, signifying that your PCV valve may be faulty.

Oil leaks or increased oil consumption

Moisture may block the hose or PCV valve and cause high pressure to build up inside the crankcase of your BMW’s engine. In addition, it may force pressure to move from your vehicle’s gaskets from the cylinders. Signs of large oil leaks and high consumption of oil are also indicative of a faulty PCV valve.

Exhaust emitting blue, black, or white smoke

A blocked PCV valve may force oil into your BMW’s combustion chambers, thus, causing oil to burn inside the BMW’s engine and leave through the vehicle’s exhaust pipe. You may notice a high amount of blue smoke from the exhaust pipe. A faulty PCV valve that produces a lean or rich mixture may cause the exhaust pipe to produce black or white smoke.

Contaminated filter

A failing or faulty PCV valve may cause oil and hydrocarbon to contaminate the breather element or filter. An increase in pressure buildup in the BMW’s crankcase may force water vapor to move through the filter. As a result, a mixture of gas and water may cause high fuel consumption.

To diagnose this issue, you should check if your vehicle’s filter is contaminated through physical inspection. You can also diagnose a faulty BMW PCV valve by measuring your vehicle’s gas mileage. If your BMW’s gas reduces without obvious reasons, the fault may be from a failing PCV valve.

Poor vehicle performance

A failing PCV valve may affect the overall performance of your vehicle. Issues such as excess oil consumption, black, blue, or white smoke emissions, a contaminated filter, high idle rpms, and more are associated with a faulty PCV valve. These symptoms consequently affect your BMW’s overall performance.

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* BMW Car image credit goes to: vesilvio.