Tools and materials needed:
- Spark plugs (Recommended: Motorcraft SP-410)
- Spark plug socket wrench
- Extension bar
- Ratchet wrench
- Gapping tool (if necessary)
- Dielectric grease
Steps:
1. Turn off the engine and allow it to cool down. Work on a cold engine to avoid burns.
2. Locate the spark plugs. They are located on the top of the engine, usually towards the front. There are eight spark plugs in total, two for each cylinder.
3. Remove the spark plug wires. Use the spark plug socket wrench to carefully loosen and remove the spark plug wires from the spark plugs. Be careful not to pull on the wires too hard as they can be damaged.
4. Check the spark plugs. Inspect the old spark plugs for wear or damage. If the electrodes are worn or cracked, they need to be replaced.
5. Gap the new spark plugs. If the new spark plugs are not pre-gapped, use a gapping tool to adjust them to the specified gap. The correct gap for a 1999 F-150 5.4L Triton is 0.054 inches.
6. Install the new spark plugs. Hand-tighten the new spark plugs until they are snug. Then, use the ratchet wrench and extension bar to tighten the spark plugs further. Tighten them until they are snug, but do not over-tighten.
7. Reattach the spark plug wires. Make sure to attach the wires to the correct spark plugs. The firing order for a 1999 F-150 5.4L Triton is 1-3-7-2-6-5-4-8.
8. Start the engine to check for proper function. Once you have installed the new spark plugs and reattached the wires, start the engine to check for proper function. Listen for any unusual noises or vibrations. If everything seems fine, take your vehicle for a test drive to ensure that the spark plugs are working properly.
Additional Tips:
- Apply a small amount of dielectric grease to the spark plug threads before installing them. This helps prevent corrosion and makes it easier to remove them in the future.
- Replace all eight spark plugs at once for optimal performance.
- If you encounter any difficulties or have concerns about performing this task, it's best to consult with a professional mechanic.
