Complete replacement of all six ignition coils on the 3.5L EcoBoost V6 engine, including spark plug inspection and torque verification.

Warnings

Tools required

Parts

• Ignition coil × 6 — Motorcraft DG-521 or equivalent
• Spark plug × 6 — Motorcraft SP-546 (if replacing)

Preparation

1. Park vehicle on level surface and engage parking brake
2. Allow engine to cool completely (minimum 2 hours after operation)
3. Disconnect negative battery cable and wait 5 minutes for capacitor discharge
4. Remove engine cover by pulling upward on front edge to release clips, then lifting entire cover off
5. Label each coil connector or take photos to ensure correct reassembly order (cylinders 1-3 on passenger side, 4-6 on driver side)

Procedure

1. 1

   Disconnect electrical connectors
   Press down on the locking tab of each ignition coil connector and pull straight up to disconnect. Work methodically from front to back on each bank. The connectors have a positive lock and require firm pressure on the release tab.
2. 2

   Remove ignition coil retaining bolts
   Using a 7mm socket, remove the single bolt securing each ignition coil. Keep bolts organized by cylinder position if wear is uneven. These are thread-forming bolts that thread directly into the valve cover.
3. 3

   Extract ignition coils
   Grasp each coil firmly and pull straight up with a twisting motion to break the seal. The coil boot may stick to the spark plug. If a coil is difficult to remove, gently twist while pulling upward. Do not pry against the valve cover as it is plastic and can crack.
4. 4

   Clean spark plug wells
   Use compressed air to blow out any debris from each spark plug well before removing plugs. Direct air around the spark plug to force debris upward and out. Any dirt or debris that falls into the cylinder can cause damage.
   ⚠Do not allow any foreign material to enter the combustion chamber. Even small debris can cause cylinder damage.
5. 5

   Remove spark plugs
   Using a 5/8" spark plug socket, carefully remove all six spark plugs. Turn counterclockwise slowly for the first few turns to avoid cross-threading. Inspect each plug for unusual wear, oil fouling, or damage which may indicate engine problems. Keep plugs in order if diagnosing engine issues.
6. 6

   Inspect spark plug condition
   Examine electrode wear, insulator color, and gap. Normal plugs show light tan/gray deposits. Black sooty deposits indicate rich condition, white/blistered indicates lean or overheating. Oil fouling suggests ring or valve seal issues. Replace plugs if in doubt or per maintenance schedule.
7. 7

   Install spark plugs
   Apply a thin coat of anti-seize compound to the threads of each new or cleaned spark plug, avoiding the electrode end. Hand-thread each plug carefully to avoid cross-threading in the aluminum heads. Once finger-tight, use the torque wrench to tighten to specification.
   ⚠️Cross-threading spark plugs in aluminum heads requires expensive head repair. Always start plugs by hand and ensure they thread smoothly.
   Torque spec

   Spark Plugs - Aluminum Head20 Nm (15 lb-ft)
8. 8

   Prepare new ignition coils
   Inspect new coil boots for damage. Apply a thin layer of dielectric grease inside each coil boot to aid installation and future removal. This also improves the electrical connection and prevents moisture intrusion.
9. 9

   Install ignition coils
   Align each coil over its corresponding spark plug and press down firmly with a twisting motion until the coil boot seats fully on the plug. The coil should sit flush against the valve cover. You should feel the boot snap onto the spark plug terminal.
10. 10

    Install ignition coil bolts
    Thread each coil retaining bolt by hand first to ensure proper alignment. Using a torque wrench and 7mm socket, tighten all six bolts to specification in any order. Do not over-torque as the plastic valve cover threads can strip.
    Torque spec

    Ignition Coil Bolts8 Nm (6 lb-ft)
11. 11

    Reconnect electrical connectors
    Push each coil connector straight down onto its coil until you hear and feel a positive click. Gently tug upward on each connector to verify it is fully locked. Verify each connection matches your reference photos or labels.
12. 12

    Reinstall engine cover and battery
    Position engine cover over the engine, aligning rear clips first, then pressing down firmly on all mounting points until all clips engage. Reconnect negative battery cable and tighten securely.

Reassembly

1. Ensure all six coil electrical connectors are fully seated and locked
2. Verify engine cover is properly clipped in place on all mounting points
3. Double-check that no tools or parts remain in engine bay

Verification

• Turn ignition to ON position without starting and verify no check engine light related to ignition system
• Start engine and listen for smooth idle with no misfires or rough running
• Allow engine to reach operating temperature and verify smooth acceleration with no hesitation
• Scan for diagnostic trouble codes using OBD-II scanner to confirm no misfire codes (P0300-P0306)
• Perform a test drive under various loads to confirm proper operation and throttle response

More procedures for this vehicle