Nissan Pick-ups and Pathfinder 1970-1988

PCV Valve


See Figure 1

The PCV valve regulates crankcase ventilation during various engine operating conditions. At high vacuum (idle speed and partial load range) it will open slightly and at low vacuum (full throttle) it will open fully. This causes vapor to be removed from the crankcase by the engine vacuum and then sucked into the combustion chamber where it is burned.

The PCV system will not function properly unless the oil filler cap is tightly sealed. Check the gasket on the cap and be certain it is not leaking. Replace the cap, gasket or both to ensure proper sealing.


  1. Check the ventilation hoses and lines for leaks or clogging. Clean or replace as necessary.
  3. With the engine running at idle, locate the PCV valve then remove the ventilation hose from the valve; a strong hissing sound should be heard as air passes through the valve.
  5. With the engine still idling, place your finger over the valve; a strong vacuum should be felt.
  7. If the PCV valve failed either of the preceding two checks, it will require replacement.
  9. Locate the PCV valve in the cylinder head cover or intake manifold and remove it by unscrewing it and then pulling it upward.

To install:
  1. Slip the hose back onto the proper end of the PCV valve and then press it into the retaining grommet or screw it back in.
  3. An additional check without removing the valve could be: with the engine running, remove the ventilator hose from the PCV valve. If the valve is working, a hissing noise will be heard as air passes through the valve and a strong vacuum should be felt immediately when the valve inlet is blocked with a finger. If the valve is suspected of being plugged, it should be replaced.
  5. For further information on the PCV system, please refer to Driveability & Emissions Controls .

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Fig. Fig. 1: A strong suction should be felt when a finger is placed over the PCV valve with the engine idling