This procedure covers the removal and replacement of spark plugs on the 3.5L V6 EcoBoost engine in a 2021-2024 Ford F-150.

Warnings

Tools required

Parts

• Spark plugs (V6 EcoBoost application) × 6 — Motorcraft SP-546 or equivalent iridium plugs
• Ignition coil boots (if damaged) × 6 — Inspect and replace as needed

Preparation

1. Ensure engine is completely cold to the touch, especially turbochargers
2. Disconnect negative battery cable to prevent accidental cranking
3. Remove engine cover by releasing retaining clips and lifting upward
4. Photograph or label ignition coil connections for proper reassembly
5. Have new spark plugs ready and verify correct gap specification (typically 0.030-0.032 inches for EcoBoost)

Procedure

1. 1

   Remove engine cover and access components
   Release the engine cover clips by pulling upward on the cover. On some models, you may need to disconnect a quick-release vacuum line at the rear of the cover. Set the cover aside in a clean area.
   Torque spec

   Engine Cover Clips3 Nm (2 lb-ft)
2. 2

   Disconnect electrical connectors from ignition coils
   Locate all six ignition coils - three on each cylinder bank. Press the locking tab on each electrical connector and pull straight up to disconnect. On the passenger side, you may need to move wiring harnesses or brackets for better access.
3. 3

   Remove ignition coils from driver side bank (cylinders 1, 2, 3)
   Using a 10mm socket, remove the single bolt securing each ignition coil. Gently twist and pull upward on each coil to break the seal with the spark plug. If coils are stuck, use a gentle twisting motion - do not pry against the valve cover. Set coils aside in order.
   Torque spec

   Ignition Coil Bolt12 Nm (9 lb-ft)
4. 4

   Remove ignition coils from passenger side bank (cylinders 4, 5, 6)
   Repeat the coil removal process for the passenger side. Access is more restricted due to turbocharger proximity. You may need longer extensions to reach the bolts. Be careful not to damage turbo heat shields or vacuum lines.
   ⚠Passenger side has limited clearance near turbocharger. Work carefully to avoid damaging heat shields or oil feed lines.
   Torque spec

   Ignition Coil Bolt12 Nm (9 lb-ft)
5. 5

   Clean spark plug wells
   Use compressed air to blow out any debris from each spark plug well. Dirt or oil in the wells can fall into the cylinder during plug removal, causing engine damage. If oil is present in the wells, inspect valve cover gaskets for leaks.
   ⚠Any debris that falls into the cylinder can cause serious engine damage. Ensure wells are completely clean before removing plugs.
6. 6

   Remove old spark plugs
   Using a 5/8" spark plug socket with appropriate extensions, carefully loosen each spark plug. Turn counterclockwise approximately 1/4 turn to break the seal, then unscrew completely by hand if possible. Remove all six plugs and inspect for abnormal wear, oil fouling, or carbon buildup.
7. 7

   Inspect old plugs and cylinder condition
   Examine each plug electrode for normal wear. All plugs should show similar wear patterns. Uneven wear, oil deposits, or excessive carbon may indicate engine issues. Use a flashlight to visually inspect each cylinder through the spark plug hole for obvious damage or debris.
8. 8

   Prepare new spark plugs
   Verify the gap on each new spark plug using a gap tool - should typically be 0.030-0.032 inches (verify specification for your specific application). Apply a thin coat of anti-seize compound to the threads of each plug, being careful not to get any on the electrode or insulator. Avoid overtightening by using anti-seize.
   ⚠Do not apply anti-seize to the electrode or insulator as this will cause misfires. Apply only to the threads.
9. 9

   Install new spark plugs
   Carefully thread each new spark plug by hand into the cylinder head. Turn clockwise until finger-tight to ensure proper threading. Use extreme care not to cross-thread the plugs. Once hand-tight, use the torque wrench and spark plug socket to tighten to specification. Because anti-seize is used and these are aluminum heads, use the lower 20 Nm (15 lb-ft) specification.
   ⚠️Cross-threading or overtightening spark plugs in aluminum heads will strip the threads and require thread repair or head replacement. Start each plug by hand to ensure proper threading.
   Torque spec

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

    Reinstall ignition coils - driver side
    Inspect each ignition coil boot for cracks or damage. Apply a small amount of dielectric grease to the inside of each boot. Align each coil over its corresponding spark plug and push down firmly until it seats. Install and hand-tighten the mounting bolt, then torque to specification using a 10mm socket.
    Torque spec

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

    Reinstall ignition coils - passenger side
    Repeat the coil installation process for the passenger side bank. Ensure each coil is fully seated before tightening the bolt. Double-check that no vacuum lines or wiring was pinched during installation.
    Torque spec

    Ignition Coil Bolt12 Nm (9 lb-ft)
12. 12

    Reconnect electrical connectors
    Reconnect the electrical connector to each ignition coil, ensuring each connector clicks into place and is fully seated. Verify connections match your reference photos from disassembly. Route any displaced wiring harnesses back to their original positions.
13. 13

    Reinstall engine cover and reconnect battery
    Position the engine cover and press down firmly on all clip locations until each clips seats with an audible click. Reconnect any vacuum lines that were disconnected. Reconnect the negative battery cable.
    Torque spec

    Engine Cover Clips3 Nm (2 lb-ft)

Reassembly

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

Verification

• Start the engine and allow it to idle - it should start immediately and run smoothly without misfires
• Listen for any unusual sounds such as vacuum leaks or rattles that might indicate improper reassembly
• Use a scan tool to verify no misfire codes are present (P0300-P0306)
• Allow engine to reach operating temperature and verify smooth idle and normal acceleration
• Check for any fuel smell or visible leaks around the spark plug wells
• Test drive the vehicle and verify improved throttle response and smooth operation under load

More procedures for this vehicle