If an engine is idling rough, check for a clogged positive crankcase ventilation (PCV) valve or plugged hose. Replace as required. Use the following procedure:

1. Remove the PCV valve.
2. Run the engine at idle.
3. Place your thumb over the end of the valve to check for a vacuum. If there is no vacuum at valve, check for plugged hoses, manifold port, or PCV valve. Replace plugged or deteriorated hoses.
4. Turn OFF the engine and remove the PCV valve. Shake the valve and listen for the rattle of the needle inside the valve. If the valve does not rattle, replace the valve.

With this system, any blow-by in excess of the system capacity, from a badly-worn engine, sustained heavy load, is exhausted into the air cleaner and is drawn into the engine through the throttle body.

Proper operation of the PCV system is dependent upon a sealed engine. If oil sludging or dilution is noted, and the PCV system is functioning properly, check the engine for possible cause, such as missing oil cap, or dipstick, infrequent oil changes, internal coolant leak, and correct to ensure that system will function as intended.