Mitsubishi Car 1999-05

Positive Crankcase Ventilation (PCV) System

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Description & Operation



All engines are equipped with the Positive Crankcase Ventilation (PCV) system. The PCV system vents crankcase gases into the engine air intake where they are burned with the fuel and air mixture. The PCV system keeps pollutants from being released into the atmosphere. It also helps to keep the engine oil clean, by ridding the crankcase of moisture and corrosive fumes. The PCV system consists of the PCV valve, the nipple in the air intake and the connecting hoses.



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Fig. Typical PCV system airflow



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Fig. The PCV valve can be found either threaded to the valve cover . . .



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Fig. . . . or mounted in a grommet on the valve cover

Incorrect operation of the PCV system can cause multiple driveability symptoms.

A plugged valve or hose may cause:



Rough idle
 
Stalling or slow idle speed
 
Oil leaks
 
Sludge in engine
 

A leaking valve or hose would cause:



Rough idle
 
Stalling
 
High idle speed
 

Diagnosis & Testing



  1. Disconnect the ventilation hose from the PCV valve. Remove the PCV valve from the engine. Once removed, reconnect the ventilation hose to the valve.
  2.  
  3. Start the engine and allow to idle. Place a finger over open end of the PCV valve. Make sure intake manifold vacuum is felt on finger.
  4.  
  5. If vacuum is not felt, the PCV valve may be restricted.
  6.  



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Fig. With the engine idling, check the end of the PCV valve to see if vacuum is present

  1. Turn the engine OFF and remove the PCV valve from the hose.
  2.  
  3. Insert a thin stick into the threaded end of the PCV valve. Push on the inner plunger and inspect for movement.
  4.  



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Fig. Inspect the PCV valve for inner plunger movement. If the plunger is bound or sticking, replace the valve

  1. If plunger inside the PCV valve is not free to move back and forth, the valve is clogged and will require replacement.
  2.  


NOTE
It is possible to clean the valve using the appropriate solvent, but replacement is recommended.

Removal & Installation





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Fig. Grasp the valve and gently remove it from the valve cover



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Fig. Twist and pull on the valve to remove it from the hose



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Fig. Inspect the grommet and replace if cracked or leaking oil

  1. Disconnect the negative battery cable.
  2.  
  3. If necessary for access, remove the air intake hose and air cleaner assembly.
  4.  
  5. If necessary, unfasten the retaining clamp, then disconnect the ventilation hose from the PCV valve.
  6.  
  7. Remove the PCV valve from the camshaft (rocker) cover.
  8.  

To install:

  1. Install the PCV valve into the rocker cover. If the valve is threaded, tighten the valve until snug.
  2.  
  3. Reconnect the ventilation hose to the valve.
  4.  
  5. If removed, install the air intake hose and the air cleaner assembly.
  6.  
  7. Connect the negative battery cable.
  8.  

 
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