Replace spark plugs on the 3.5L V6 EcoBoost engine to restore ignition performance and fuel efficiency.

Warnings

Tools required

Parts

• Spark plugs (copper core recommended) × 6 — Motorcraft SP-546 or equivalent

Preparation

1. Ensure engine is completely cold (below 100°F/38°C).
2. Park vehicle on level surface and engage parking brake.
3. Disconnect negative battery terminal to prevent accidental cranking.
4. Remove engine cover by releasing plastic clips at front and lifting rearward.
5. Verify replacement spark plugs match OEM specification for the EcoBoost engine.

Procedure

1. 1

   Prepare and gap new spark plugs
   Check and adjust gap on all six new spark plugs to 0.035" (0.9mm) using a spark plug gap tool. Apply a thin coat of anti-seize compound to the threads of each spark plug, being careful not to get any on the electrode or insulator. This is critical for aluminum heads to prevent thread galling and allow future removal.
2. 2

   Remove driver side ignition coils (cylinders 1, 2, 3)
   Locate the three ignition coils on the driver side of the engine. Disconnect the electrical connector from each coil by pressing the release tab and pulling straight up. Remove the single 10mm bolt securing each coil (torque spec: 8.0 Nm on reassembly). Grasp each coil firmly and pull straight up with a twisting motion to remove. Mark coil positions if desired for reinstallation order.
   Torque spec

   Ignition Coil Bolt12 Nm (9 lb-ft)
3. 3

   Remove driver side spark plugs
   Use compressed air or a vacuum to clean debris from around each spark plug well to prevent contamination from falling into the cylinder. Using a 5/8" spark plug socket with at least a 6" extension, carefully loosen each spark plug. Turn counterclockwise slowly - if excessive resistance is felt, stop and verify engine is completely cold. Remove plugs completely and inspect for unusual wear patterns or oil fouling.
   ⚠If plugs show oil fouling or excessive carbon buildup, investigate for underlying engine problems before completing installation.
4. 4

   Install driver side spark plugs
   Carefully start each new spark plug by hand in the spark plug well, turning clockwise. Thread at least 3-4 full turns by hand to ensure proper thread engagement - this prevents cross-threading. Use the spark plug socket and torque wrench to tighten to exactly 20.0 Nm (15 lb-ft). Do not exceed this torque specification on aluminum heads.
   Torque spec

   Spark Plug23 Nm (17 lb-ft)
5. 5

   Reinstall driver side ignition coils
   Apply a small amount of dielectric grease to the inside of each coil boot. Push each ignition coil straight down into the spark plug well until it seats fully on the spark plug. Install the 10mm mounting bolt and torque to 8.0 Nm (6 lb-ft). Reconnect the electrical connector to each coil until it clicks into place.
   Torque spec

   Ignition Coil Bolt12 Nm (9 lb-ft)
6. 6

   Access passenger side ignition coils
   On the passenger side, access is more restricted due to brake booster and HVAC components. You may need to work around the charge air cooler outlet pipe. Identify cylinders 4, 5, and 6 coils along the passenger side valve cover.
7. 7

   Remove passenger side ignition coils (cylinders 4, 5, 6)
   Disconnect the electrical connector from each of the three passenger side coils. Remove the single 10mm bolt from each coil. Pull each coil straight up with a twisting motion. The rear coil (cylinder 6) may require a longer extension or universal joint for access. Clean around spark plug wells with compressed air.
   Torque spec

   Ignition Coil Bolt12 Nm (9 lb-ft)
8. 8

   Remove passenger side spark plugs
   Using the 5/8" spark plug socket with a 10" extension and possible universal joint for cylinder 6, carefully remove each spark plug. The rear plug may require working at an angle due to firewall clearance. Turn counterclockwise slowly and verify no binding occurs. Remove and inspect all three plugs.
9. 9

   Install passenger side spark plugs
   Carefully start each new spark plug by hand, turning clockwise. Thread at least 3-4 full turns by hand before using any tools. This is especially critical on the rear plug where visual confirmation of proper threading is difficult. Torque each plug to exactly 20.0 Nm (15 lb-ft) using the torque wrench.
   Torque spec

   Spark Plug23 Nm (17 lb-ft)
10. 10

    Reinstall passenger side ignition coils
    Apply dielectric grease to coil boots. Push each ignition coil straight down until fully seated on the spark plug. Install and torque the 10mm mounting bolts to 8.0 Nm (6 lb-ft). Reconnect all electrical connectors ensuring they click into place. Verify all connections are secure.
    Torque spec

    Ignition Coil Bolt12 Nm (9 lb-ft)
11. 11

    Reinstall engine cover and reconnect battery
    Position the engine cover over the engine, aligning the rear mounting points first. Press down on clip locations until all clips engage fully. Reconnect the negative battery terminal. The vehicle computer may need to relearn idle characteristics over the first few drive cycles.

Reassembly

1. Double-check all six ignition coil electrical connectors are fully seated and locked.
2. Verify engine cover is properly clipped at all mounting points.
3. Confirm no tools or parts were left in the engine bay.

Verification

• Start the engine and verify it runs smoothly without misfires or rough idle.
• Allow engine to idle for 2-3 minutes and listen for any unusual sounds.
• Use an OBD-II scanner to verify no misfire codes (P0300-P0306) are present.
• Test drive the vehicle and confirm normal acceleration and no hesitation under load.
• After first drive cycle, visually inspect ignition coils to ensure they remain properly seated.

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