The PCV valve is an often ignored yet critical component of a vehicle’s emission system. PCV valve stands for positive crankcase ventilation valve. And its acronym means exactly what it states. The valve vents gases from the crankcase when proper circumstances warrant. A pcv valve is usually attached to a valve cover and helps to scavenge blow by gases from the combustion process. Blow-by is burnt combustion gases occurring from the combustion cycle that happen to squeeze through the piston ring and cylinder wall interface, making their way into your oil reservoir system. A very small percentage of total combustion gases actually make it through the piston rings as blow-by but over time the effect is cumulative. As such a system was needed to remove these gases which are full of hydrocarbon unconverted by the catalytic converters.
Enter PCV valve. The pcv valve actually allows these trapped crankcase vapors to move out of the crankcase and back into the intake manifold to mix with incoming air. Thus they are given another chance to combust in the cylinder chamber and go out the exhaust pipe like they were originally supposed to. The net effect of the PCV valve is thus a decrease in vehicle hydrocarbon emissions.
Over time the PCV valve can become clogged or seize up due to hardened oil sludge buildup within it. At this point the PCV may not open fully or when it is supposed to. In addition the valve may seize completely shut and never allow any blow-by gases to escape the oil sump system at all. The net effect of this is a degradation of your oil quality through oxidation of the oil with blow-by gases. This will cause your oil to sludge up, lose its flow and cooling characteristics, and need to be replaced much more often than normal. Low oil quality can contribute to reduced fuel economy.
In today’s heavily computer controlled and adjusted vehicles a malfunctioning PCV valve can cause non optimal tuning characteristics via your engine’s management system that can contribute to reduced power and reduced fuel economy. Thus it is very important to check you PCV valve and replace it on a high mileage vehicle as it is often ignored.
1. Usually you can remove your PCV valve and inspect it for proper operation by shaking and listening for the valve movement, a type of clicking noise. If you do not hear it making noise then it is most likely seized. There is also another way to check with the motor running by pinching the PCV valve tube hose and listening for the clicking sound coming from the PCV.
2. Generally it is a good rule of thumb if you are in question to replace the PCV as it is such a cheap accessory part that it is not worth fooling around with trying to clean it or inspect it.