The Lincoln Navigator is a full sized V-8 SUV with a 5.4-liter engine. This power house engine is capable of pulling that large SUV down the road. However, at about the 100,000-mile mark, the spark plugs will begin to wear out. This will cause the engine to lose horsepower, and you will notice your vehicle feeling sluggish as you drive. Replacing the plugs and wires will help you regain that lost power from your Navigator.
Locate spark plugs 1 through 4 on the driver's side of the engine then locate spark plugs 5 through 8 on the passenger's side of the engine. The spark plugs thread into the engine head, and each of them has a large, black rubber boot connected to them. From that boot, a wire extends to the distributor cap.
Twist the black rubber boot on the spark plug closest to the front of the engine while pulling up on the boot to pop it off the spark plug wire. Remove the other end of the wire from the distributor cap in the same manner.
Place a socket extension bar onto the ratchet then connect a spark plug socket to the end of the extension bar. Remove the spark plug from the engine head with the ratchet by turning the spark plug counterclockwise.
Thread the replacement spark plug into the engine head with your fingers. Tighten the spark plug a 1/4-turn with the ratchet.
Place the boot of the spark plug wire over the spark plug then push down on the boot until you feel it snap onto the spark plug wire.
Place the boot on the other end of the wire on the distributor and attach it in the same manner as the other boot.
Repeat this same process for the other seven spark plugs, working your way from front to back on the driver's side then from front to back on the passenger's side.
