Spark Plugs

Replace spark plugs on the 2018-2024 Honda Accord 1.5L turbo engine to restore ignition performance and maintain engine efficiency.

Warnings

Tools required

Parts

• Spark plugs (iridium or platinum) × 4 — NGK DILKAR8H8S or Honda OEM 9807B-5617W

Preparation

1. Ensure engine is completely cool to the touch
2. Park vehicle on level surface and engage parking brake
3. Gather all tools and new spark plugs before beginning
4. Verify new spark plugs match OEM specifications for this engine

Procedure

1. 1

   Remove engine cover
   Grasp the front edge of the plastic engine cover and pull upward firmly to release the mounting clips. The cover is held by push clips only on this model. Set aside in a clean area.
   Torque spec

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

   Disconnect ignition coil connectors
   Locate all four ignition coils on top of the valve cover. Press the release tab on each coil electrical connector and pull straight up to disconnect. The connectors are color-coded and can only be reinstalled one way.
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. Note that some model years may use slightly different bolt lengths.
   Torque spec

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

   Extract ignition coils
   Pull each ignition coil straight up and out of the spark plug well with a firm, steady motion. If coils are stuck, gently twist while pulling. Inspect coil boots for cracks or deterioration and replace if damaged.
5. 5

   Clean spark plug wells
   Use compressed air or a clean shop towel to remove any debris, oil, or dirt from around each spark plug and inside the plug wells. This is critical to prevent contamination from entering the combustion chamber during plug removal.
   ⚠If oil is present in spark plug wells, valve cover gaskets and spark plug tube seals may need replacement. Address oil leaks before installing new plugs.
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 for unusual wear, fouling, or damage which may indicate engine issues.
7. 7

   Gap new spark plugs
   Check the gap on each new spark plug using a gap tool. Factory gap should be 0.028-0.031 inches (0.7-0.8mm) for this engine. Verify against the specifications on the spark plug box. Adjust if necessary by carefully bending the ground electrode.
   ℹ️Many iridium and platinum plugs come pre-gapped. Do not force gap adjustment on precious metal electrodes as they can break.
8. 8

   Apply anti-seize (optional)
   If using anti-seize compound, apply a very small amount only to the threads of each spark plug, avoiding the electrode end. Use sparingly as excess can contaminate the combustion chamber. Anti-seize is optional on aluminum heads but can aid future removal.
   Torque spec

   Spark Plug20 Nm (15 lb-ft)
9. 9

   Install new spark plugs
   Carefully thread each spark plug by hand into the cylinder head, ensuring it starts smoothly without resistance. If resistance is felt, back out and restart to avoid cross-threading. Once hand-tight, use the torque wrench to tighten to specification. Install all four plugs to proper torque.
   ⚠️Cross-threading spark plugs will damage aluminum cylinder head threads, requiring expensive repair or thread insert installation. Always start by hand.
   Torque spec

   Spark Plug20 Nm (15 lb-ft)
10. 10

    Reinstall ignition coils
    Apply a thin coat of dielectric grease to the inside of each coil boot if desired. Push each ignition coil firmly into its spark plug well until fully seated on the spark plug. The coil should sit flush with the valve cover surface.
11. 11

    Install ignition coil bolts
    Install the 10mm bolt for each ignition coil and tighten to specification using the torque wrench. Do not over-tighten as the valve cover is aluminum.
    Torque spec

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

    Reconnect electrical connectors
    Push each ignition coil electrical connector onto its corresponding coil until you hear and feel a positive click. Verify each connector is fully seated by gently tugging on the connector body.
13. 13

    Reinstall engine cover
    Align the engine cover mounting clips with their receptacles on the engine. Press down firmly at each clip location until all clips are fully engaged and the cover sits flush.
    Torque spec

    Engine Cover Clips3 Nm (2 lb-ft)

Reassembly

1. Double-check that all four ignition coil electrical connectors are fully seated and locked
2. Verify engine cover is securely clipped in place at all mounting points
3. Ensure no tools or parts were left in the engine compartment

Verification

• Start the engine and verify it runs smoothly without misfires or rough idle
• Check for diagnostic trouble codes using an OBD-II scanner if check engine light illuminates
• Listen for unusual noises that could indicate improperly seated ignition coils
• Allow engine to reach operating temperature and verify smooth acceleration with no hesitation

More procedures for this vehicle