by Jody L. Campbell
A positive crankcase ventilation (PCV) valve is a useful device that is one of the oldest emission control components in most vehicles. It returns the partially burned gases from the crankcase through the one-way valve into the combustion chamber for re-burning. Although different vehicles position the PCV valve differently, it should be fairly easy to find. The tube that runs from the intake manifold to the valve cover contains the PCV valve. On most vehicles, it is located on top of the valve cover, but some models require the removal of other components to access it.