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Positive Crankcase Ventilation (PCV) system removes harmful gases from the engine’s crankcase and burns those gases in the cylinders. Positive crankcase ventilation devices allow the venting of combustion gases from the crankcase to the intake system instead of into the atmosphere.

  • Filtered air from the air cleaner is drawn through the crankcase by intake manifold vacuum. The air pickups the blowby gas or vapors and carries them to the intake manifold.
  • The gas vapors then flow through the intake manifold to the combustion chambers. There the unburned fuel burn during normal combustion
  •  Toom much air flowing through the intake manifold during idling can upset the air-fuel ratio which can cause poor idling engine stalling or rough idling.
  • A fixed orifice or variable orifice flow control valve enables to prevent and develop these types of vehicle problems.
  • As the engine speed increases reduced intake manifold vacuum allows the valve to open further which then allows more air to flow through.
  • In a worn or defective engine, more blowby may enter the crankcase that can flow through the PCV valve.
  • The excess blowby flows back through the tube to the air cleaner instead of escaping to the outside air.