Models with partial zero-emissions vehicle (PZEV) engines are equipped with an air filter that is designed to last the life of the vehicle. If service becomes necessary, a qualified repair facility should be consulted. The air filter cannot be cleaned and should be replaced if dirty. On models through 2002, the air cleaner is in the engine compartment. On 2003 and later 2.3L engines and all 2005 models, the air cleaner is located in the left fender-well. For 2.0L models (through 2004), remove the screws securing the air filter box lid, raise the filter housing cover and pull out the filter element. Installation is the reverse of removal. For 2.3L and 2005 and later 2.0L models, remove the left fender well liner, disconnect the electrical connector at the MAF sensor, remove the bolts and loosen the clamp to disconnect the air inlet pipe, remove the bolts and lower the air cleaner box, open the box and replace the filter. On 2003 and later models with the 2.3L Zetec engine, the filter and housing are replaced as a unit. Installation is the reverse of removal. Inspect the rubber seal on the air cleaner element. Replace the element if the seal is worn or damaged. Also replace the filter if replacement is indicated on the maintenance schedule or if it is so dirty that you can't clearly see the light from a flashlight held against the opposite side. Clean the inner sealing surface between the air cleaner housing and cover. Before installing the new air filter, check it for deformed seals and holes in the paper if the filter is marked TOP, be sure the marked side faces up. The remainder of installation is the reverse of the removal steps.