For 1990-2009 cars

Important: Engine blow-by gases in excess of the positive crankcase ventilation (PCV) system's capacity can deposit oil in the air cleaner. Check for a badly worn engine.

Proper operation of the PCV system is dependent upon a sealed engine. A vehicle with a PCV system that passes this functional check may have a PCV valve with an incorrect flow rate or a leak in the crankcase. Replace the PCV valve or inspect the engine's seals and gaskets if the engine uses excessive amounts of oil.

1. Disconnect the PCV valve vacuum hose at the valve cover.
2. Start the engine.
3. Run the engine at idle.
4. Place your thumb over the end of the PCV valve vacuum hose in order to check for vacuum.

• | Repair the source vacuum supply if no vacuum is felt.

• | Replace the PCV valve if the source vacuum supply is adequate.

5. Turn OFF the ignition.
6. Remove the PCV valve.
7. Shake the PCV valve while listening for the rattle of the plunger inside.
8. Replace the PCV valve if the valve does not rattle.