The PCV valve, which is the heart of the positive crankcase ventilation system, should be free of dirt and residue and in working order. As long as the valve is kept clean and is not showing signs of becoming damaged or gummed up, it should work properly. When the valve cannot be cleaned sufficiently or becomes sticky and will not operate freely, it should be replaced.
The PCV filter, which is located at the air filter housing on some 6-cylinder models, should be checked along with the PCV valve. Just blow out the screen with compressed air in the reverse direction of the normal air flow. Check to see that the screen forms a good seal around the edges of the air cleaner housing so no dirt can pass. If the screen is torn or clogged, or if it is seated improperly and cannot be repaired, replace it.
The PCV valve is in the right rocker arm (valve) cover on the V6 engines, in the intake manifold on the 4-cylinder engines, and in the rocker arm cover on the inline 6-cylinder engines.