How to check pcv valve
The purpose of a PCV valve is to collect blowby gases caused by power stroke. A small percent of gases escape through the piston ring and into the crankcase. The gas is reburn to prevent air pollution.
Symptom of a bad PCV valve:
Symptom #1 rough engine idle caused by a vacuum leak in the PCV system. This produce lean air fuel mixture.
Symptom #2 Engine surge at idle (idle speed goes up and down). This surge can cause enrich fuel mixture and emit black smoke.
To perform a quick test:
Test #1 Remove the PCV valve out of the engine valve cover or intake manifold and give it a good shake. If the PCV valve does not rattle, the PCV valve is bad.
Test #2 Feel the PCV with the hose still attached to the valve cover or intake manifold. Put your finger on the end of the PCV valve and you should feel suction. If no suction is felt, then the PCV is plugged up with sludge.