This procedure covers the replacement of spark plugs on the 2015-2020 Ford F-150 3.5L V6 EcoBoost engine, including removal of engine covers and ignition coils.

Warnings

Tools required

Parts

• Spark plugs - Motorcraft SP-546 or equivalent iridium × 6 — Motorcraft SP-546

Preparation

1. Ensure engine is completely cool to the touch
2. Disconnect negative battery cable to prevent accidental ignition system activation
3. Verify you have correct spark plugs for EcoBoost application (SP-546 or equivalent)
4. Gap new spark plugs to 0.030-0.032 inches before installation
5. Apply thin coat of anti-seize compound to spark plug threads (avoid getting on electrodes)

Procedure

1. 1

   Remove engine cover
   Grasp the engine cover firmly and pull upward to release the retention clips. The cover is held by push-clips only and does not require tools for removal. Set cover aside in clean area.
2. 2

   Remove acoustic cover (if equipped)
   Some models have an additional acoustic cover over the intake manifold. Remove the fasteners using 7mm socket and lift cover away. Store fasteners in labeled container.
   Torque spec

   Cover Screws12 Nm (9 lb-ft)
3. 3

   Disconnect ignition coil electrical connectors
   Locate all six ignition coils on top of each cylinder. Press down on the connector release tab and pull connector straight off each coil. Mark or photograph connector positions if they are not keyed differently.
4. 4

   Remove ignition coils - Bank 1 (passenger side)
   Remove the single 10mm bolt securing each ignition coil on the passenger side bank (cylinders 1, 2, 3). Grasp coil firmly and pull straight up with slight twisting motion to break seal. If coil is stuck, use needle nose pliers on the coil boot, not the coil body.
   ⚠Do not pry on ignition coils. Cracking the coil housing will cause misfires and require replacement.
   Torque spec

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

   Remove ignition coils - Bank 2 (driver side)
   Remove the single 10mm bolt securing each ignition coil on the driver side bank (cylinders 4, 5, 6). Pull coils straight up with twisting motion. Driver side may have limited access due to turbocharger and charge air cooler piping.
   Torque spec

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

   Clean spark plug wells
   Use compressed air or vacuum to remove any debris, dirt, or oil from each spark plug well. Any contamination that falls into the cylinder can cause damage. Inspect for oil pooling which may indicate valve cover gasket leakage.
   ⚠Oil or debris entering the combustion chamber can cause engine damage. Ensure wells are completely clean before removing plugs.
7. 7

   Remove old spark plugs
   Using 5/8" spark plug socket with extension, carefully loosen each spark plug. Turn counterclockwise 1-2 turns initially, then if no resistance is felt, remove completely. Remove all six plugs and place in order for inspection.
   ⚠If excessive resistance is felt when loosening, stop and apply penetrating oil. Allow to soak. Forced removal can strip aluminum threads.
8. 8

   Inspect old spark plugs
   Examine each plug for wear patterns, carbon buildup, oil fouling, or abnormal electrode wear. Consistent abnormal wear across multiple cylinders may indicate tuning, fuel quality, or mechanical issues requiring diagnosis before proceeding.
9. 9

   Install new spark plugs - Bank 1
   Install pre-gapped and anti-seized spark plugs into passenger side cylinders (1, 2, 3). Thread by hand first to ensure proper engagement. Once hand-tight, torque to specification using aluminum head torque value. Do not over-torque.
   ⚠Use aluminum head torque specification. Over-torquing will strip threads in aluminum cylinder head.
   Torque spec

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

    Install new spark plugs - Bank 2
    Install pre-gapped and anti-seized spark plugs into driver side cylinders (4, 5, 6). Thread by hand first, then torque to aluminum head specification. Verify each plug is properly seated before final torquing.
    Torque spec

    Spark Plug23 Nm (17 lb-ft)
11. 11

    Reinstall ignition coils
    Apply small amount of dielectric grease to inside of each coil boot if desired. Push each coil firmly into spark plug well until fully seated. Install and torque 10mm mounting bolts. Ensure coils are pushed down fully before tightening bolts.
    ℹ️Coil must be fully seated on spark plug before tightening bolt or poor connection will result.
    Torque spec

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

    Reconnect electrical connectors
    Push each ignition coil electrical connector onto its corresponding coil until a positive click is felt. Verify each connection is secure by gently pulling on connector body, not wires.
13. 13

    Reinstall covers
    If acoustic cover was removed, reinstall and torque fasteners. Align engine cover with mounting clips and press down firmly until all clips engage with audible clicks.
    Torque spec

    Cover Screws12 Nm (9 lb-ft)

    Engine Cover Clips3 Nm (2 lb-ft)
14. 14

    Reconnect battery and verify
    Reconnect negative battery cable. Start engine and verify smooth operation with no misfires. Check for diagnostic trouble codes. Allow engine to reach operating temperature and verify no misfires occur under load.

Reassembly

1. Ensure all ignition coil connectors are fully seated and locked
2. Verify engine cover clips are all properly engaged
3. Double-check that no tools or parts were left in engine bay

Verification

• Start engine and listen for smooth idle with no misfires or rough running
• Scan for diagnostic trouble codes - there should be no ignition-related codes
• Test drive vehicle and verify smooth acceleration with no hesitation or misfires under load
• Re-check for codes after test drive to ensure no delayed misfire detection

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