If an engine is idling rough, check for a clogged PCV valve. Replace if required. Use the following procedure:

1. Check the PCV valve (1), hoses (2), and connections for leaks or restrictions.
2. At idle, listen to the PCV valve (1) with a stethoscope as you lightly pinch the PCV hose (2) with your fingers or pliers for several times. Each time the hose is pinched, the valve should click.
3. If there is no clicking should, check the PCV valve grommet for cracks or damage. If the grommet is OK, replace the PCV valve and recheck.

With this system, any blow-by in excess of the system capacity is exhausted into the intake manifold and is drawn into the engine. Proper operation of the crankcase ventilation system is dependent upon a sealed engine. If oil sludging or dilution is noted, and the crankcase ventilation system is functioning properly, check engine for possible cause and correct to ensure that the system will function as intended.