To maintain the efficiency of the PCV system, clean the hoses and check the PCV valve at the intervals recommended in the maintenance schedule. Locate the PCV valve. On four-cylinder EFI engines, the air cleaner assembly must be removed to gain access to the PCV valve. To check the valve, first pull it out of the grommet in the rocker arm cover or manifold, or out of the lower hose. Shake the valve. It should rattle, indicating that it is not clogged with deposits. If the valve does not rattle, replace it with a new one. If it does rattle, reinstall it. Start the engine and allow it to idle, then disconnect the PCV hose. If vacuum is felt, the PCV/valve system is working properly. If no vacuum is felt, the oil filler cap, hoses or rocker arm cover gasket may be leaking or the PCV valve may be bad. Check for vacuum leaks at the valve, filler cap and all hoses. Pull straight up on the valve to remove it. Check the rubber grommet for cracks and distortion. If it's damaged, replace it. If the valve is clogged, the hose is also probably plugged. Remove the hose and clean it with solvent. After cleaning the hose, inspect it for damage, wear and deterioration. Make sure it fits snugly on the fittings. If necessary, install a new PCV valve. The elbow is not part of the PCV valve. A new valve will not include the elbow. The original must be transferred to the new valve. If a new elbow is purchased, it may be necessary to soak it in warm water for up to an hour to slip it onto the new valve. Do not attempt to force the elbow onto the valve or it will break. Install the clean PCV system hose. Make sure the PCV valve and hose are secure.