Positive Crankcase Ventilation (PCV) helps in minimizing the emission of hydrocarbons due to crankcase vapors to the atmosphere; Fresh air is circulated through PCV valve from the air cleaner goes to crankcase, mixes blow-by gases and is sent to the intake manifold through the PCV system. The major parts of the PCV system are the PCV valve, which is mounted on the valve cover and both hoses; one of the hose links the air intake duct to the valve cover housing where it provides fresh air to the crankcase and the other links the valve cover PCV valve to the air intake plenum where it carries the crankcase emission of the engine. During the deceleration and idle when intake vaccum is high, the PCV valve minimizes the amount of crankcase emissions for richness of the mixture to achieve good idle quality. On the other hand, when the throttle valve is open during acceleration and steady cruising speed the PCV valve opens further to allow the flow. When there are other irregular operations like damaged piston rings then the blow-by gases have direct access to the crankcase vent hose then to the take-air duct. Operation checks and replacement of the PCV valve and the filter are among the required regular services.