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

Warnings

Tools required

Parts

• Ignition coil × 6 — Motorcraft DG521 or equivalent
• Spark plug × 6 — Motorcraft SP546 or equivalent

Preparation

1. Ensure engine is completely cool to the touch
2. Disconnect negative battery cable and wait 2 minutes for capacitor discharge
3. Remove engine cover by pulling upward on clip fasteners
4. Clean any debris from valve cover area to prevent contamination

Procedure

1. 1

   Access driver side ignition coils
   Locate the three ignition coils on the driver side cylinder bank (cylinders 1, 2, 3). Move any wiring harnesses or hoses aside for clearance. The coils are positioned directly on top of the valve cover.
2. 2

   Disconnect driver side coil connectors
   Press the locking tab on each ignition coil electrical connector and pull straight up to disconnect. Wiggle gently if connectors are tight, but do not pull on the wires themselves.
3. 3

   Remove driver side coil mounting bolts
   Using a 10mm socket, remove the single bolt securing each ignition coil to the valve cover. Keep bolts organized for reinstallation.
   Torque spec

   Ignition Coil Bolts8 Nm (6 lb-ft)
4. 4

   Extract driver side ignition coils
   Grasp each coil firmly and pull straight up with a twisting motion to break the seal. The coil boot extends into the spark plug well. Inspect boots for tears or oil contamination.
5. 5

   Remove driver side spark plugs
   Use compressed air to blow out any debris from the spark plug wells. Insert 5/8-inch spark plug socket with extension and remove each spark plug. Check electrode condition and gap on removed plugs to verify engine condition.
   Torque spec

   Spark Plugs - Aluminum Head20 Nm (15 lb-ft)
6. 6

   Access passenger side ignition coils
   Move to the passenger side of the engine. The passenger side may have additional wiring or coolant hoses that need to be moved aside for access to cylinders 4, 5, and 6.
7. 7

   Disconnect passenger side coil connectors
   Press the locking tab on each ignition coil electrical connector and pull straight up to disconnect. Follow the same procedure as the driver side.
8. 8

   Remove passenger side coil mounting bolts
   Using a 10mm socket, remove the single bolt securing each ignition coil to the valve cover on the passenger side.
   Torque spec

   Ignition Coil Bolts8 Nm (6 lb-ft)
9. 9

   Extract passenger side ignition coils
   Remove all three passenger side coils using the same twisting and pulling motion. Inspect boots for damage or oil contamination indicating potential valve cover gasket issues.
10. 10

    Remove passenger side spark plugs
    Clean spark plug wells with compressed air, then remove all three passenger side spark plugs with the 5/8-inch spark plug socket. Inspect plugs for wear patterns.
    Torque spec

    Spark Plugs - Aluminum Head20 Nm (15 lb-ft)
11. 11

    Install new spark plugs
    Apply a small amount of anti-seize compound to the threads of each new spark plug. Hand-thread each plug to prevent cross-threading, then torque to specification. Install all six plugs across both banks.
    Torque spec

    Spark Plugs - Aluminum Head20 Nm (15 lb-ft)
12. 12

    Prepare new ignition coils
    Apply a thin layer of dielectric grease inside the boot of each new ignition coil to aid in future removal and prevent moisture intrusion. Ensure coil boots are clean and properly seated on the coil body.
13. 13

    Install new ignition coils
    Insert each coil into its spark plug well, ensuring the boot fully seats onto the spark plug terminal. Align the mounting bolt hole and press down firmly until the coil seats against the valve cover. Install and torque all six coil mounting bolts.
    Torque spec

    Ignition Coil Bolts8 Nm (6 lb-ft)
14. 14

    Reconnect electrical connectors
    Push each electrical connector onto its corresponding coil until the locking tab clicks into place. Tug gently on each connector to verify it is locked.
15. 15

    Complete installation
    Reinstall engine cover by aligning clips and pressing down firmly. Reconnect negative battery cable. Clear any stored diagnostic codes if applicable.

Reassembly

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

Verification

• Start engine and listen for smooth idle with no misfires or rough running
• Verify no check engine light illumination after 30 seconds of running
• Rev engine gently to 2000-3000 RPM to confirm all cylinders are firing properly
• Scan for diagnostic trouble codes to confirm no misfire codes are present
• Perform a test drive to verify smooth acceleration and no hesitation under load

More procedures for this vehicle