Replace spark plugs on a 2014-2019 Toyota Corolla 1.8L I4 engine to restore ignition performance and fuel efficiency.

Warnings

Tools required

Parts

• Spark plugs (iridium) × 4 — 90919-01253 or equivalent

Preparation

1. Ensure engine is completely cold 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 spark plug gap specification (typically 0.043 inches for this engine)

Procedure

1. 1

   Remove engine cover
   Grasp the plastic engine cover at the front corners and pull upward firmly to release the retaining clips. The cover is friction-fit and does not require tools to remove.
2. 2

   Remove ignition coil connectors
   Locate the four individual ignition coils on top of the engine. Press the locking tab on each electrical connector and pull straight up to disconnect. Keep track of which connector goes to which cylinder position.
3. 3

   Remove ignition coils
   Use a 10mm socket to remove the single bolt securing each ignition coil. Pull each coil straight up and out of the spark plug tube. Inspect coil boots for damage or oil contamination.
   ⚠If coil boots are oil-soaked, inspect valve cover gasket for leaks before proceeding
   Torque spec

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

   Clean spark plug wells
   Use compressed air or a shop vacuum to remove any debris from the spark plug tubes. Debris falling into the cylinders during plug removal can cause serious engine damage.
   ⚠️Do not allow any foreign material to fall into the cylinder when spark plugs are removed
5. 5

   Remove old spark plugs
   Using a 5/8" spark plug socket with extension, carefully loosen each spark plug by turning counterclockwise. Once loose, unthread by hand and remove. Inspect old plugs for abnormal wear, fouling, or damage which may indicate engine problems.
6. 6

   Prepare new spark plugs
   Check and adjust the gap on each new spark plug to specification (typically 0.043 inches) using a spark plug gap tool. Apply a small amount of anti-seize compound to the threads of each plug, avoiding the electrode area.
   ℹ️Do not apply anti-seize to the electrode or insulator as this can cause misfires
7. 7

   Install new spark plugs
   Start each spark plug by hand into the cylinder head, turning clockwise. Thread in at least 3-4 full turns 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.
   ⚠If plug does not thread smoothly by hand, remove and restart - do not force
   Torque spec

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

   Reinstall ignition coils
   Apply a thin coat of dielectric grease to the inside of each coil boot if desired. Push each coil firmly into its spark plug tube until fully seated. Install and torque the 10mm mounting bolt on each coil.
   Torque spec

   Ignition Coil Bolt10 Nm (8 lb-ft)
9. 9

   Reconnect electrical connectors
   Push each electrical connector onto its corresponding ignition coil until the locking tab clicks into place. Gently tug on each connector to verify secure connection.
10. 10

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

Reassembly

1. Ensure all electrical connectors are fully seated and locked
2. Verify engine cover is secure and all clips are properly engaged
3. Double-check that no tools or materials were left in the engine bay

Verification

• Start the engine and verify smooth idle with no misfires or rough running
• Check for diagnostic trouble codes using an OBD-II scanner if check engine light illuminates
• Listen for any unusual sounds from the ignition coil or spark plug area
• Test drive vehicle to confirm normal acceleration and performance under load

More procedures for this vehicle