Jeep Wagoneer/Commando/Cherokee 1984-1998

Positive Crankcase Ventilation (PCV) System


See Figures 1 and 2

The PCV valve, which is the heart of the positive crankcase ventilation system, should be inspected every 60,000 miles (96,000 km) and replaced, if necessary. The main thing to keep in mind is that the valve must be free of dirt and residue to stay in working order. As long as the valve is clean and is not showing signs of becoming damaged or clogged, it should perform its function properly. When the valve becomes sticky and will not operate freely, it should be replaced.

The PCV valve is used to control the rate at which crankcase vapors are returned to the intake manifold. The action of the valve plunger is controlled by intake manifold vacuum and the spring. During deceleration and idle, when manifold vacuum is high, it overcomes the tension of the valve spring and the plunger bottoms in the manifold end of the valve housing. Because of the valve construction, it reduces, but does not stop, the passage of vapors to the intake manifold. When the engine is lightly accelerated, or operated at constant speed, spring tension matches intake manifold vacuum pull and the plunger takes a mid-position in the valve body, allowing more vapors to flow into the manifold.

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Fig. Fig. 1: View of the vapor flow through a PCV valve

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Fig. Fig. 2: Common PCV valve and hose location

Removal & Installation

See Figure 3

  1. Remove the PCV valve from cylinder head.
  3. Remove the PCV valve from PCV hose.
  5. Installation is the reverse of removal.

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Fig. Fig. 3: Removing the PCV valve from the PCV hose