2016-2021 Honda Civic 10th Gen - Spark Plug Change

1

Cool the engine

Work only on a cold engine. Hot aluminum heads can pull threads when plugs are removed. Disconnect the negative battery terminal if you want extra safety around coils.

2

Access the ignition coils

Remove any engine cover or intake tube blocking the coils. Label coil connectors or photograph the layout so each coil returns to the same cylinder.

3

Remove one coil at a time

Unplug the coil connector, remove the coil hold-down bolt, and pull the coil straight up. Work one cylinder at a time so dirt cannot fall into open plug wells.

4

Remove the old spark plug

Blow loose dirt from the well. Use a spark-plug socket with a rubber insert and extension to remove the plug. Inspect the tip for oil, coolant, or abnormal wear.

5

Gap and hand-thread the new plug

Confirm the new plug part number and set the gap to the manufacturer specification if required (many iridium plugs are pre-gapped — check carefully). Start threading by hand or with a swivel extension to avoid cross-threading.

6

Torque to specification

Torque the plug to the spec in the service information (typically a modest ft-lb or degree value). Overtightening cracks the ceramic or stretches the shell.

7

Reinstall the coil

Press the coil fully onto the plug, reinstall the hold-down bolt to snug/spec, and reconnect the electrical connector until it locks. Repeat for remaining cylinders.

8

Reassemble and test

Refit covers/intake components, reconnect the battery if removed, and start the engine. Listen for misfires and clear any codes if a coil was left unplugged during the job.