Replace all six spark plugs on the 3.5L EcoBoost V6 engine, including removal of intake components and ignition coils to access the plugs.

Warnings

Tools required

Parts

• Spark plugs × 6 — Motorcraft SP-546 or equivalent iridium
• Anti-seize compound × 1 — Use nickel-based anti-seize

Preparation

1. Ensure engine is completely cold to the touch
2. Park vehicle on level surface and engage parking brake
3. Disconnect negative battery cable to prevent accidental cranking
4. Remove engine cover by pulling upward on cover to release clips
5. Gather all tools and new spark plugs, verify correct part number

Procedure

1. 1

   Remove air intake system
   Disconnect the air intake tube from the throttle body by loosening the hose clamp. Remove the entire air filter housing assembly by disconnecting the electrical connector on the mass airflow sensor and removing mounting bolts. Set aside to provide access to the front bank spark plugs.
2. 2

   Remove charge air cooler tubes
   Loosen clamps and disconnect the charge air cooler tubes running across the top of the engine. These tubes connect the turbochargers to the intercooler and intake manifold. Carefully move them aside to access the rear bank ignition coils. Note their routing for reassembly.
3. 3

   Remove ignition coils from front bank (passenger side)
   Disconnect the electrical connector from each of the three front ignition coils by pressing the release tab. Remove the single 7mm bolt securing each coil. Carefully pull each coil straight up and out of the spark plug well. Mark or note the cylinder position of each coil.
   Torque spec

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

   Remove front bank spark plugs
   Use compressed air or a vacuum to clean debris from around each spark plug well. Insert the 5/8 inch spark plug socket with extension and carefully loosen each plug. If significant resistance is felt, stop and apply penetrating oil, then wait 15 minutes. Remove plugs completely and inspect for oil fouling or abnormal wear.
5. 5

   Remove ignition coils from rear bank (driver side)
   Disconnect electrical connectors from the three rear ignition coils. Remove the 7mm retaining bolt from each coil. Pull each coil straight up from the spark plug well. These may be more difficult to access due to limited space near the firewall.
   Torque spec

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

   Remove rear bank spark plugs
   Clean around each rear spark plug well. Use extensions and possibly a universal joint to access the rear plugs with the spark plug socket. Carefully loosen and remove each plug. Exercise extra caution as these plugs are more prone to seizing due to heat from the turbos.
   ⚠Rear bank plugs run hotter due to proximity to turbochargers and are more likely to seize. Apply extra care during removal
7. 7

   Inspect old spark plugs and cylinder heads
   Examine all six removed plugs for wear patterns, electrode erosion, carbon buildup, or oil fouling. Use a flashlight to inspect inside each spark plug well for any debris, oil, or coolant. Clean wells thoroughly if needed before installing new plugs.
8. 8

   Prepare new spark plugs
   Verify the spark plug gap on all six new plugs using a gap tool. The specified gap for this engine is typically 0.030-0.035 inches - verify against the plug manufacturer specification. Apply a small amount of nickel-based anti-seize compound to the threads of each plug, coating approximately 2/3 of the threads. Do not allow anti-seize on the electrode end.
   ℹ️Anti-seize is critical on aluminum heads to prevent future seizure, but use sparingly to avoid contamination
9. 9

   Install front bank spark plugs
   Carefully thread each new spark plug by hand into the front bank cylinders, ensuring they start straight and thread smoothly. Once hand-tight, use the torque wrench and spark plug socket to tighten to the specified torque of 20 Nm (15 lb-ft) for aluminum heads. Do not over-tighten.
   Torque spec

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

    Install rear bank spark plugs
    Hand-thread each rear bank spark plug carefully, ensuring proper alignment. Tighten to 20 Nm (15 lb-ft) using the torque wrench. The limited access makes it crucial to ensure the socket is properly seated on the plug during torquing.
    Torque spec

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

    Reinstall ignition coils
    Apply a thin coat of dielectric grease to the inside of each ignition coil boot if desired. Install each coil into its corresponding cylinder, ensuring it seats fully onto the spark plug. Install and torque the 7mm retaining bolt on each coil to 8 Nm (6 lb-ft). Reconnect all electrical connectors, ensuring they click into place.
    Torque spec

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

    Reinstall charge air cooler tubes and intake system
    Reinstall the charge air cooler tubes in their original routing, tightening all hose clamps securely. Reinstall the air filter housing and intake tube, reconnecting the mass airflow sensor electrical connector. Ensure all clamps are tight and no vacuum leaks are present.
13. 13

    Reinstall engine cover and reconnect battery
    Align the engine cover with the mounting clips and press down firmly until all clips engage. Reconnect the negative battery cable. The vehicle may need to relearn idle characteristics during the first few starts.

Reassembly

1. Ensure all electrical connectors are fully seated with audible clicks
2. Verify all hose clamps on intake and charge air tubes are tightened properly
3. Double-check that no tools or parts were left in the engine bay
4. Confirm engine cover is securely clipped in all positions

Verification

• Start the engine and listen for smooth idle with no misfires or rough running
• Check for any vacuum leaks around intake connections - listen for hissing sounds
• Verify no check engine light or misfire codes are present
• Road test the vehicle under light acceleration to confirm smooth operation
• Inspect for any visible leaks around spark plug wells after test drive
• Monitor engine performance for the first 50-100 miles as the ECU adapts

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