2019 Ford 3.5L EcoBoost Spark Plugs and Coil Packs Advice at 81,000 Miles

Changing spark plugs on your 2019 Ford F-150 3.5L EcoBoost at 81,000 miles is a solid maintenance move. The plugs are likely due or close to it, depending on your exact service history. Coil packs don’t have a fixed replacement interval but should be tested and replaced if faulty or showing signs of wear. The #1 cause of comebacks here is oil leaks from old spark plug tube seals and improper torque causing thread damage or misfires. Be sure to replace the spark plug tube seals every time you remove plugs—this is critical to prevent oil contamination and future issues.

What you'll need

• Tools:

  • 10mm and 8mm sockets (for coil pack bolts and spark plug tube seal bolts)
  • Spark plug socket (5/8" or 13/16" depending on plug)
  • Torque wrench (0-150 ft-lbs range)
  • Ratchet and extensions
  • Pick tool or seal puller (for removing old tube seals)
  • Compressed air or blower (to clean plug wells)

• Parts & consumables:

  • OEM or equivalent spark plugs (check exact part number for 2019 3.5 EcoBoost)
  • Spark plug tube seals (replace all 6)
  • Anti-seize compound (sparingly on plug threads)
  • Dielectric grease (for coil boots)

• Optional:

  • Ignition coil packs (only if testing shows failure or misfire codes persist)
  • Spark plug gap tool (verify gap if plugs aren’t pre-gapped)

Step-by-step

1. Prep: Disconnect negative battery terminal for safety.

2. Remove engine cover: Usually held by clips or bolts.

3. Access coils: Remove coil pack bolts (usually 10mm), then gently pull coils straight up.

4. Remove spark plug tube seals: Use a pick or seal puller to carefully remove old seals from the spark plug wells.

5. Clean plug wells: Blow out any debris or oil from the wells to prevent it falling into the cylinder when plugs come out.

6. Remove spark plugs: Use spark plug socket and extension; turn counterclockwise carefully.

7. Inspect coils: Check coil boots for cracks or corrosion. If damaged or if you have misfire codes, replace coils.

8. Install new tube seals: Press new seals fully into place in the plug wells.

9. Install new spark plugs: Apply a small amount of anti-seize on plug threads (avoid the electrode and gasket area). Thread plugs by hand to avoid cross-threading, then torque to spec.

10. Apply dielectric grease: Lightly inside coil boots.

11. Reinstall coils: Bolt down to spec.

12. Reinstall engine cover and reconnect battery.

13. Start engine and check for smooth running and no misfire codes.

Specs & resets

• Spark plug torque: 13 Nm (9.5 ft-lbs) — do not overtighten.
• Coil pack bolt torque: 10 Nm (7.4 ft-lbs).
• Use Motorcraft or equivalent spark plugs specified for 2019 3.5L EcoBoost.
• Spark plug gap: Usually pre-gapped, verify 0.028-0.031 inches (check exact OEM spec).
• No special reset needed unless you have a check engine light; then clear codes after repair.

Common mistakes to avoid

• Not replacing spark plug tube seals: Leads to oil leaks and fouled plugs.
• Cross-threading spark plugs: Always start by hand to avoid damaging cylinder head threads.
• Overtorquing plugs: Can strip aluminum heads or break plugs.
• Not cleaning plug wells: Dirt or oil can fall into cylinders causing damage.
• Ignoring coil condition: Bad coils cause misfires even with new plugs.

A few questions

• Have you had any recent misfire codes or rough running?
• Are you planning to replace all plugs or just some?
• Do you have OEM spark plugs or aftermarket?
• Have you noticed any oil leaks around the spark plug wells?
• Do you have the proper torque wrench and spark plug socket?

If you want, I can help you with coil testing procedures or plug part numbers.