At the specified intervals, the air filter and, if equipped, the PCV filter should be replaced with new ones, as the engine air cleaner supplies filtered air to the PCV system. Carbureted and TBI models can be identified by a Z in the eighth position of the Vehicle Identification Number (VIN). To replace the filter, remove the engine cover, then locate the filter on top of the carburetor or Throttle Body Injection unit. Unscrew the wing nut from the top of the filter housing and lift off the cover, taking care not to drop anything into the carburetor, TBI, or air cleaner assembly. Lift the air filter element out of the housing and wipe out the inside of the air cleaner housing with a clean rag before placing the new filter in, ensuring it seats properly. The PCV filter may also be located inside the air cleaner housing on some models; after removing the top plate and air filter, locate and remove the old PCV filter, then install the new PCV filter and air filter. Finally, reinstall the top plate and any disconnected hoses, followed by the engine cover. For Central Multiport Fuel Injection and Central Sequential Fuel Injection models, identifiable by a W or X in the eighth position of the VIN, loosen the clamp screw on the intake air duct and disconnect it from the air filter cover. Detach the clips securing the air filter cover and remove it, then lift the filter out of the housing, noting the direction of installation. Installation is the reverse of removal, with many replacement filters marked with an arrow to indicate the airflow direction.