Positive Crankcase Ventilation: Testing and Inspection

A quick check of the system can be made by pulling end of valve out of valve cover and, then with engine idling, placing a finger over end of valve to block air flow. A strong vacuum should be felt and engine speed should drop if the system is performing satisfactorily. If there is no change in engine speed, a clogged system is indicated.

To isolate problem, remove PCV valve from hose. If hoses and passages are clear, a strong vacuum will be felt with the engine idling. Engine idle will change drastically and the engine may stall when the hose is uncovered. If this occurs, the trouble is in the valve. If the engine continues to idle approximately as it did before the hose was uncovered, the hoses or passages are blocked.