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1984‐1998 Jeep Emission Controls Crankcase Ventilation System (PCV/CCV)

Jeep Wagoneer/Commando/Cherokee 1984‐1998

Emission Controls

Crankcase Ventilation System (PCV/CCV)


PCV Valve

To inspect the PCV valve, remove the valve from the rocker arm cover hose, then shake it. If the valve rattles, it is probably fine; if there is no sound, it must be replaced and the PCV hose cleaned by spraying solvent (such as a carburetor cleaner type of solvent) through it. 

If the valve rattles, you should still check the PCV valve with the engine idling. Pull it out of the vent module and place your finger or thumb over the end to stop air flow. You should feel some suction, and the engine speed should drop slightly. If there is no suction, or if the engine idle speeds up and smooths out considerably, replace the valve. Remove the PCV hose from the engine, then inspect it and, if the inside is coated with gum and varnish, clean it by spraying solvent through it.

Check the vacuum at the PCV inlet (from the rocker arm cover to the air cleaner) tube, as well. Disconnect this tube from the air cleaner and loosely hold a piece of paper over the tube. After a few seconds (10-15 seconds), enough vacuum should build up to cause the paper to be sucked against the opening with a noticeable amount of force. This test proves whether or not the suction side of the system is clear. Download File PDF

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