The 2004 Ford Mustang comes in several different models, the most common being the Mustang GT and the Mustang Fastback. The engine on the Mustang GT is a 5.0-liter V8 engine with eight spark plugs. The Mustang Fastback has a 4.0-liter V6 engine or smaller. The spark plugs are located on the right and left sides of the engine and have rubber-covered wires over the ends of the spark plugs. On both of these Mustang models the new spark plugs will need to be gapped to the specification for that model. The process for replacing spark plugs on both of these models will be the same.
Open the hood of the 2004 Ford Mustang and locate the spark plugs on the right and left side of the engine. If you can't find them, then follow the wires from the distributor cap down to the spark plugs.
Pull the rubber-covered wires off of the ends of each spark plug. Connect the socket to the ratchet and remove the spark plug from the engine using the ratchet and socket.
Gap all of the new spark plugs to the specifications for your Mustang model (see Tip below). Insert the new spark plug into the engine and tighten the plugs using the ratchet and socket. Replace the wires at the ends of the spark plugs and close the hood.
