Changing spark plugs in a six-cylinder Mitsubishi Galant should be done routinely to keep the engine running properly. Replacing the spark plugs is part of the tune-up process and should be done about once every six months, depending on how much you drive the vehicle. The spark plugs are located on the side of the engine block below the valve cover and can be changed in about an hour or two with some basic tools.
Remove the engine cover from the top of the Galant by unfastening the bolt that secures the cover with a socket wrench. Lift the cover off the motor and set it out of the way.
Locate the spark plugs on the side of the motor, underneath the valve cover. The spark plugs have a spark plug wire extending from each plug to the distributor.
Remove the spark plug wire off of the end of the spark plug on one end of the motor by pulling it straight out and setting it aside. Loosen the spark plug with a spark plug puller, gently turning the plug counterclockwise to prevent breaking the plug.
Lift the spark plug out of the motor and discard the old plug. Set the gap on the end of the new spark plug with a spark plug gapper according to the settings in the Mitsubishi Galant owner's manual.
Insert the new spark plug into the engine where you removed the old spark plug and turn the plug clockwise until it is hand-tight, without over-tightening the plug. Tightening the plug too much can result in cracking the spark plug casing. Connect the spark plug wire to the end of the new spark plug.
Repeat Steps 1 through 5 for each of the remaining spark plugs. Reattach the engine cover to the top of the motor.
