How do you replace a fuel injector on a 1994 Nissan Altima?

The fuel injectors are located behind the valve cover toward the firewall and are secured to the fuel rail by two screws and a cap. Remove the electrical connector, screws and cap. (If screws are difficult to remove, try soaking the screws in penetrating oil or follow the tip below.) The theory is to twist, rock and turn while pulling slightly upwards. Look at the top of the injectors, they have holes on both sides, grip the sides with a pair of bent needle nose Vise-Grip pliers. Lock it on with just enough pressure to grip the sides of the injector firmly, too much and you'll break the plastic. Gently rotate and rock the injector back and forth while gently prying it upward between the fuel rail and the pliers with a bladed screwdriver. Once you get them out, use brand new O-Rings smeared them with Vaseline before re-inserting. They will snap back into the rails and lock into the O-Ring grooves. Make sure you spin them around to make sure the O-Rings are seated in the grooves and are not pinched. Replace the cap, screws and electrical connectors. ------------------------------------------------ LITTLE TIP TO HELP GET THOSE STUBBORN SCREWS OUT ------------------------------------------------ To get the screws off, get a center punch. Get a small hammer and start tapping at the screw using the center punch from different directions. Put some penetrating fluid and keep on tapping. You are trying to loosen up the screw from the threads.