Spark Plug Wires

This procedure covers the inspection and replacement of ignition coils on the 2018-2024 Honda Accord 1.5L Turbo engine, which uses a coil-on-plug design without traditional spark plug wires.

Warnings

Tools required

Parts

• Ignition coil (if faulty) × 4 — Honda 30520-5AA-A01 or equivalent
• Spark plugs × 4 — NGK DILKAR8A8S or equivalent iridium

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 terminal and wait 3 minutes
4. Gather all tools and parts before beginning
5. Verify replacement spark plugs match OEM specification for this engine

Procedure

1. 1

   Remove engine cover
   Grasp the engine cover firmly at the front edge and pull upward to release the retaining clips. The cover is held by push-clips and does not require tool removal. Set cover aside on a clean surface.
2. 2

   Locate ignition coils
   Identify all four ignition coils mounted directly on top of the cylinder head. They are rectangular units with electrical connectors on top, located along the intake side of the engine. Note their positions for reassembly.
   ℹ️The coils are numbered 1-4 from the timing belt end to the transmission end of the engine.
3. 3

   Disconnect ignition coil electrical connectors
   Press the locking tab on each ignition coil connector and pull straight up to disconnect. Do not pull on the wires themselves. Work from cylinder 1 to cylinder 4 to maintain organization.
   ⚠Connectors may be stiff. Use controlled force and ensure tab is fully depressed before pulling.
4. 4

   Remove ignition coil mounting bolts
   Using a 10mm socket with extension, remove the single mounting bolt from each ignition coil. Keep bolts organized to ensure they return to their original locations. The bolts are located at the top center of each coil.
5. 5

   Extract ignition coils
   Grasp each ignition coil firmly and pull straight up with a twisting motion to break the seal. The coil boot extends into the spark plug well and may stick due to heat cycling. Do not use excessive force that could damage the coil boot.
   ⚠If coil is stuck, twist gently while pulling. A stuck coil boot that tears will require complete coil replacement.
6. 6

   Inspect spark plug wells
   Check each spark plug well for oil, coolant, or debris accumulation. If oil is present, valve cover gasket replacement is required before continuing. Remove any debris with compressed air or a clean lint-free cloth.
   ⚠Oil in spark plug wells indicates a failing valve cover gasket and will cause premature ignition coil failure if not addressed.
7. 7

   Remove spark plugs
   Using a spark plug socket with extension, carefully remove each spark plug by turning counterclockwise. Keep plugs in order to allow inspection of individual cylinder combustion conditions. Inspect each plug for wear, fouling, or abnormal deposits.
8. 8

   Prepare new spark plugs
   Verify the spark plug gap on all new plugs using a gap tool. Factory gap should be 0.028-0.031 inches (0.7-0.8mm). Apply a small amount of anti-seize compound to the threads only, avoiding the electrode area. Use anti-seize sparingly to prevent over-torquing.
   ⚠Excessive anti-seize can cause spark plugs to exceed torque specification and damage aluminum threads.
9. 9

   Install new spark plugs
   Thread each spark plug by hand to ensure proper alignment and prevent cross-threading. Once hand-tight, use the torque wrench and spark plug socket to tighten to specification. Work from cylinder 1 to cylinder 4.
   ⚠️Over-torquing spark plugs in aluminum heads can strip threads, requiring expensive thread repair or cylinder head replacement.
10. 10

    Inspect and prepare ignition coils
    If reusing original coils, inspect each coil boot for cracks, tears, or carbon tracking. Apply a thin layer of dielectric grease to the inside of each coil boot to prevent moisture intrusion and ensure proper electrical connection. If installing new coils, apply dielectric grease to boots before installation.
    ℹ️Replace any coil showing signs of physical damage or arcing. Damaged coils will cause misfires.
11. 11

    Install ignition coils
    Align each ignition coil with its spark plug well and press down firmly until the coil seats completely on the valve cover. The coil boot must fully engage the spark plug terminal. Install the mounting bolt finger-tight first to ensure proper alignment.
12. 12

    Torque ignition coil bolts
    Using the torque wrench, tighten each ignition coil mounting bolt to specification. Do not over-tighten as this can crack the coil housing or damage the valve cover.
13. 13

    Reconnect electrical connectors
    Push each electrical connector onto its corresponding ignition coil until you hear and feel a positive click. Gently tug on each connector to verify it is fully seated and locked in place.
    ℹ️A loose connector will cause a misfire code and poor engine performance.
14. 14

    Reinstall engine cover
    Position the engine cover over the mounting clips and press down firmly at each clip location until all clips engage with an audible click. Verify the cover is fully seated and secure.

Reassembly

1. Reconnect negative battery terminal and tighten securely
2. Verify all electrical connectors are properly seated
3. Ensure no tools or parts have been left in the engine compartment

Verification

• Start the engine and verify smooth idle with no misfires or rough running
• Check for any diagnostic trouble codes using an OBD-II scanner
• Listen for any unusual ignition-related noises such as arcing or ticking
• Allow engine to reach operating temperature and verify continued smooth operation
• Perform a test drive to verify normal acceleration and power delivery under load

Related trouble codes on this vehicle

Codes that commonly send this job to the bay — tap one for symptoms, causes, and diagnostic steps.

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