PCV valve is an emission control device, which makes use of intake manifold vacuum to avoid the escape of crankcase blow-by gases into the atmosphere. During idle, the valve opens only slightly to ensure a minor entry of blow-by gas into the intake manifold, which gets mixed with intake air to be burned. With rising engine speed the valve opens even more to allow more blow-by gases into the chamber. To test the 1978-82 GLC and 1979-82 626 with the engine idling and warmed up, remove the hose connected to the PCV valve, and place a drop over the opening; a drop in idle speed indicates that it is working properly. In other models, the engine must be warmed, the PCV valve disconnected, and the opening covered, and alterations in idle speed monitored. When the idle speed decreases, then the valve is operating properly. The RX-7 lacks a PCV system and operates a vent, check valve or a check and cut valve as a means of dealing with the blow-by gases. To remove and install, first loosen the air cleaner assembly as necessary, and then loosen the hose of the PCV valve. Pre-1983 models have a threaded PCV valve screwed into the intake manifold, but newer models normally have a valve screwed into a valve cover grommet. When necessary, rotate the valve carefully and pull or unscrewed, moving any washers that are present. Installation occurs in the opposite order making sure that the two ends of the valve are correctly seated and that any hose ventilators which may have been broken are replaced.