The PCV valve is mostly found in the valve cover and can be tested by running your car to its normal operating temperature, then pulling the valve from the panel (with hose attached). You may cover this valve opening with your thumb to test for vacuum. If there is no suction, check for a plugged hose, manifold port or the valve itself and replace any plugged or deteriorated hoses. After that, shut off your engine and shake the PCV valve while listening for a rattle. Whenever it doesn't rattle you should replace it. To remove it, pull the valve out of the end of the hose noting how it has been installed in there. In order to compare them against one another ensure that you choose a replacement pcv valve that suits vehicle make as well as model. Push down until seated on all rubber hoses before checking if they are damaged or hardened otherwise; follow this up with fixing pcv valves into their correct positions!