2021 Honda Accord Spark Plugs Replacement: Tools, Steps, and What To Check First

Quick Answer

Replacing spark plugs in a 2021 Honda Accord takes 1–2 hours, depending on your engine variant (1.5L Turbo or 2.0L Turbo). You’ll need basic automotive tools and OEM-spec spark plugs (NGK ILZKAR8H8S for 1.5T, NGK ILZKR7B11 for 2.0T). Key steps: Let the engine cool completely (2+ hours), disconnect the negative battery terminal, remove ignition coils, gap new plugs to manufacturer specs (0.031–0.035 in for 1.5T; 0.043–0.047 in for 2.0T), and torque plugs to 18 ft-lbs (1.5T) or 15 ft-lbs (2.0T)—always confirm torque and gap specs with your vehicle’s official service manual for accuracy.

Before You Start

Confirm your engine variant: The 2021 Accord comes with two options: 1.5L Turbo (LX, Sport, EX, EX-L) and 2.0L Turbo (Sport, EX-L, Touring). Specs and parts vary between them.
Cool the engine: Working on a hot engine risks burns and warped components. Wait at least 2 hours after turning off the vehicle.
Prepare your workspace: Park on a flat, stable surface, engage the parking brake, and chock the rear wheels (optional but recommended).
Gather all tools and parts upfront: Avoid mid-job delays by verifying you have everything listed below.

Tools and Parts

Required Tools

3/8-inch drive ratchet
6-inch extension bar
5/8-inch spark plug socket (with rubber insert to protect plugs)
Torque wrench (calibrated to measure 10–20 ft-lbs)
Spark plug gap gauge (wire or blade type)
Dielectric grease
10mm socket (for engine cover and ignition coil bolts)
Breaker bar (optional, for stuck spark plugs)
Heat-resistant gloves and safety glasses

Recommended Parts

OEM Spark Plugs:
- 1.5L Turbo: NGK ILZKAR8H8S (Honda part # 95112)
- 2.0L Turbo: NGK ILZKR7B11 (Honda part # 93486)
Replacement ignition coils (optional, if old coils show cracks or corrosion)
Valve cover gasket (optional, if oil is present on old spark plugs)

Step-by-Step Replacement

For Both Engine Variants

Disconnect the negative battery terminal: Loosen the 10mm bolt on the negative (-) terminal, pull the cable off, and secure it away from the battery to prevent electrical shocks.
Remove the engine cover: Use a 10mm socket to unscrew the bolts holding the plastic engine cover, then lift it off.
Replace spark plugs one at a time: This avoids mixing up ignition coil wiring. Repeat steps 4–10 for each cylinder:

Cylinder-Specific Steps

Disconnect the ignition coil connector: Press the tab on the electrical connector and pull it straight off the coil.
Remove the ignition coil: Unscrew the 10mm bolt holding the coil in place, then gently pull the coil straight up (wiggle it if stuck to break free from the spark plug).
Inspect the ignition coil: Check for cracks, corrosion, or oil buildup. Replace if damaged.
Remove the old spark plug: Attach the spark plug socket and extension to the ratchet, then turn counterclockwise to loosen the plug. Pull it out carefully.
Check the old plug condition: Look for worn electrodes, black carbon deposits, or oil residue (signs of underlying issues like a valve cover leak).
Prepare the new spark plug:
- Verify the gap matches your engine’s specs (use the gap gauge to adjust if needed—pre-gapped plugs may not always be accurate).
- Apply a thin layer of dielectric grease to the inside of the ignition coil boot (prevents corrosion and improves electrical connection).
Install the new spark plug:
- Thread the plug into the cylinder head by hand to avoid cross-threading.
- Use the torque wrench to tighten to the correct spec: 18 ft-lbs (1.5T) or 15 ft-lbs (2.0T). Do not over-tighten.
Reassemble components: Push the ignition coil back into place, tighten the 10mm bolt, and reconnect the electrical connector.
Reinstall the engine cover: Align it with the mounting points and tighten the 10mm bolts.
Reconnect the battery: Attach the negative terminal cable and tighten the 10mm bolt.
Test the engine: Start the vehicle and let it idle for 5–10 minutes. Check for rough idling or misfires.

Common Mistakes to Avoid

Over-tightening spark plugs: Can strip cylinder head threads, leading to costly repairs. Always use a calibrated torque wrench.
Skipping the gap check: Pre-gapped plugs may deviate from Honda’s specs. A wrong gap causes misfires and reduced fuel efficiency.
Working on a hot engine: Risks burns and can cause the spark plug to seize in the cylinder head.
Reusing faulty ignition coils: Even new plugs won’t fix misfires caused by cracked or corroded coils. Inspect coils before reinstalling.
Mixing up coil wiring: Replacing one plug at a time ensures you don’t cross-connect coils to the wrong cylinders.

Fitment or Diagnostic Notes

Fitment confirmation: Always double-check part numbers with your Honda dealer or official service manual, as minor production changes may affect specs.
Aftermarket plugs: If using non-OEM plugs, ensure they match the OEM heat range, thread size, and gap specs to avoid engine damage.
Signs you need replacement: Rough idle, reduced fuel economy, difficulty starting, or a check engine light with misfire codes (P0300–P0304).

Safety Precautions

Wear heat-resistant gloves and safety glasses to protect against burns and debris.
Never force a stuck spark plug: Apply penetrating oil (like WD-40) and wait 15–20 minutes before attempting removal again.
Disconnect the battery before handling ignition coils to prevent accidental electrical shock.
Keep tools and parts away from moving engine components (e.g., fan belts) if the engine is running.

When To Stop and Call a Professional

If a spark plug breaks off in the cylinder head (improper removal can damage the engine block).
If you notice oil on the old spark plugs (indicates a valve cover gasket leak or internal engine issue requiring professional diagnosis).
If the check engine light remains on after replacement (may need a scan tool to reset codes or identify underlying problems).
If you’re unsure about torque specs or plug fitment—incorrect installation can lead to engine failure.