Positive Crankcase Ventilation: Testing and Inspection

Results of Incorrect Operation

1. A plugged valve or hose may cause:

^ Rough idle.
^ Stalling or slow idle speed.
^ Oil leakage.
^ Oil in air cleaner.
^ Sludge in engine.

2. A leaking PCV valve or hose will cause:

^ Rough idle.
^ Stalling.
^ High idle speeds.

Functional Check

With these systems, any blow-by in excess of the system capacity (from a badly worn engine, sustained heavy load, etc.) is exhausted into the air cleaner and is drawn into the engine.

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 and correct to ensure that the system will function as intended.

If an engine is idling rough, check for a clogged PCV valve, dirty vent filter, air cleaner element, or plugged hose. Replace as required. Use the following procedure:

1. Remove PCV valve from the rocker cover.
2. Operate engine at idle.
3. Place your thumb over the end of the valve to check for vacuum. If there is NO vacuum at the valve, check:
^ For plugged hoses.
^ Check manifold port.
^ Check PCV valve.
4. Turn "OFF" the engine and remove PCV valve. Shake the valve and listen for the rattle of the check needle inside of the valve. If it does NOT rattle, replace the valve.