Tools You'll Need:
* Socket Set: A 3/8" drive socket set with a deep well socket that fits your spark plugs (usually 5/8" for Ford). A wobble extension is highly recommended to improve access.
* Spark Plug Socket: A spark plug socket is crucial. It has a rubber insert to grip the plug without damaging it.
* Wrench: A ratchet wrench (3/8" drive) is most efficient.
* Extension: One or more extensions to reach the plugs in the back of the engine.
* Torque Wrench: Essential to avoid over-tightening or under-tightening the new plugs.
* Spark Plug Gap Tool: Use this to check and set the gap on your new spark plugs (if necessary; some come pre-gapped).
* Penetrating Oil (like PB Blaster): Helps loosen stubborn plugs.
* Gloves: To keep your hands clean.
* Jack and Jack Stands (or ramps): For easier access to the engine. Safety First: Always use jack stands when working under a vehicle.
* Shop Rags or Paper Towels: For cleaning.
* New Spark Plugs: Get the correct type for your engine. Check your owner's manual for the correct specifications.
Step-by-Step Instructions:
1. Safety First: Disconnect the negative (-) battery cable before starting any work.
2. Vehicle Preparation: Park the Expedition on a level surface, engage the parking brake, and chock the rear wheels. Raise the front of the vehicle using a jack and secure it safely on jack stands. Alternatively, use ramps.
3. Locate Spark Plugs: The spark plugs are located on top of the engine, one per cylinder (8 total). You'll need to locate them; consult your owner's manual for exact positions. The rear plugs are usually the hardest to access.
4. Preparation for Removal: Spray penetrating oil onto each spark plug well. Let it sit for 15-20 minutes to help loosen any corrosion.
5. Remove the Coil Packs (if applicable): Depending on your engine's year and configuration, you may need to remove the coil packs (the ignition coils) to access the spark plugs. These usually have bolts or clips securing them. Carefully disconnect the electrical connectors and then remove the coil packs.
6. Remove Spark Plugs: Using the spark plug socket and extension(s), carefully remove the old spark plugs. Go slowly and apply even pressure to avoid stripping the threads. If a plug is particularly stubborn, try using a little more penetrating oil and letting it sit a few more minutes. Avoid using excessive force.
7. Inspect Old Spark Plugs: Examine the old spark plugs for signs of wear, fouling, or damage. This can help you diagnose potential engine problems.
8. Install New Spark Plugs: Before installing the new spark plugs, check the gap with a spark plug gap tool (if required). Carefully screw the new plugs into the cylinder head by hand until they are snug. Then, use the spark plug socket and torque wrench to tighten them to the manufacturer's specified torque. Do not overtighten.
9. Reinstall Coil Packs (if applicable): Reinstall the coil packs, ensuring the electrical connectors are securely attached.
10. Lower Vehicle: Carefully lower the vehicle using the jack.
11. Reconnect Battery Cable: Reconnect the negative (-) battery cable.
12. Start Engine: Start the engine and listen for any unusual noises or misfires. Let it run for a few minutes.
Important Considerations:
* Torque Specifications: This is crucial. Over-tightening can damage the spark plug threads in the cylinder head, while under-tightening can lead to leaks and misfires. Consult your owner's manual for the correct torque settings.
* Plug Type: Use the exact type and heat range of spark plug recommended by Ford for your 1999 Expedition. The wrong plugs can lead to serious engine damage.
* Difficulty of Access: The rear spark plugs are often difficult to reach. Patience and the right tools are essential. A mirror or flexible inspection light can be helpful.
* Professional Help: If you are uncomfortable performing this task yourself, consider taking your Expedition to a qualified mechanic.
This detailed guide should help you, but remember that working on your vehicle involves inherent risks. If you have any doubts or concerns, it's always best to seek professional help.
