Spark Plugs - V8

Replace spark plugs on a 2016-2021 Honda Civic 1.5L turbocharged engine to restore ignition performance and fuel efficiency.

Warnings

Tools required

Parts

• Spark plugs (NGK or Denso iridium) × 4 — NGK IZFR6K13 or equivalent

Preparation

1. Park vehicle on level surface and engage parking brake
2. Allow engine to cool completely for at least 2 hours if recently driven
3. Ensure ignition is off and key is removed from vehicle
4. Gather all tools and parts before beginning

Procedure

1. 1

   Remove engine cover
   Grasp the engine cover at the front corners and pull upward firmly to release the retaining clips. The cover is held by plastic clips only on this engine.
   Torque spec

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

   Disconnect ignition coils
   Locate all four ignition coils on top of the valve cover. Press down on the locking tab of each coil electrical connector and pull straight up to disconnect. Mark or remember the cylinder order if connectors are not identical.
3. 3

   Remove ignition coil bolts
   Using a 10mm socket, remove the single bolt securing each ignition coil. Keep bolts organized as they will be reused.
   ℹ️Some coils may have 8 Nm spec bolts; verify which torque spec applies to your specific build date.
   Torque spec

   Ignition Coil Bolt10 Nm (8 lb-ft)
4. 4

   Extract ignition coils
   Grasp each ignition coil firmly and pull straight up with a gentle twisting motion. The coils are sealed with rubber boots that may resist removal. Do not pry or bend the coils.
5. 5

   Clean spark plug wells
   Use compressed air or a clean lint-free cloth to remove any debris, oil, or dirt from around each spark plug and inside the plug wells. This prevents contamination from falling into the cylinders.
   ⚠If oil is present in spark plug wells, valve cover gasket or tube seals may need replacement.
6. 6

   Remove old spark plugs
   Using the spark plug socket with extension, carefully loosen each spark plug by turning counterclockwise. Once loose, unthread by hand to prevent cross-threading. Remove all four plugs and inspect electrodes for wear, carbon buildup, or oil fouling.
7. 7

   Inspect and gap new spark plugs
   Verify new spark plugs match OEM specification (typically pre-gapped to 0.028-0.031 inches for this engine). Use gap tool to confirm proper gap. Do not adjust iridium or platinum plugs unless necessary as electrode tips are fragile.
   ℹ️Most OEM-spec replacement plugs come pre-gapped, but always verify before installation.
   Torque spec

   Spark Plug19 Nm (14 lb-ft)
8. 8

   Apply anti-seize compound
   Apply a small amount of anti-seize compound to the threads of each new spark plug. Use sparingly—only coat the first 2-3 threads. Avoid getting anti-seize on the electrode or insulator.
   ⚠Excessive anti-seize can cause over-torquing and thread damage; use only a thin coat.
   Torque spec

   Spark Plug19 Nm (14 lb-ft)
9. 9

   Install new spark plugs
   Thread each spark plug by hand into the cylinder head, turning clockwise. Ensure plugs thread smoothly without resistance. If resistance is felt, remove and restart—do not force. Once hand-tight, use torque wrench to tighten to specification.
   ⚠️Cross-threading spark plugs in aluminum heads can cause expensive engine damage requiring head removal and repair.
   Torque spec

   Spark Plug19 Nm (14 lb-ft)
10. 10

    Reinstall ignition coils
    Apply a small amount of dielectric grease to the inside of each coil boot (optional but recommended). Push each coil firmly into its spark plug well until it seats completely. Install and hand-start the retaining bolt for each coil.
11. 11

    Torque ignition coil bolts
    Using a torque wrench, tighten each ignition coil bolt to the specified torque. Work in a pattern from cylinder 1 to cylinder 4.
    Torque spec

    Ignition Coil Bolt10 Nm (8 lb-ft)
12. 12

    Reconnect electrical connectors
    Push each ignition coil electrical connector onto its coil until you hear or feel a positive click. Gently tug on each connector to verify it is locked in place.
13. 13

    Reinstall engine cover
    Align the engine cover clips with their mounting points on the valve cover and engine. Press down firmly at each clip location until all clips snap into place.
    Torque spec

    Engine Cover Clips3 Nm (2 lb-ft)

Reassembly

1. Double-check that all ignition coil connectors are fully seated and locked
2. Verify engine cover is secure at all clip points
3. Ensure no tools or parts are left in the engine bay

Verification

• Start the engine and listen for smooth, even idle with no misfires or rough running
• Check that Check Engine Light does not illuminate
• Allow engine to reach operating temperature and verify no misfires occur under light acceleration
• If available, use an OBD-II scanner to check for misfire codes (P0300-P0304)

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