This procedure covers the inspection and replacement of ignition coils on a 2014-2019 Toyota Corolla 1.8L I4 engine. Note: This engine uses individual coil-on-plug ignition coils, not traditional spark plug wires.

Warnings

Tools required

Parts

• Spark plugs × 4 — NGK or Denso Iridium, use OEM specification
• Ignition coils (if replacing) × 4 — Toyota OEM 90919-02258 or equivalent

Preparation

1. Park vehicle on level surface and engage parking brake
2. Ensure engine is completely cool to touch
3. Disconnect negative battery terminal and wait 3 minutes for airbag system to discharge
4. Verify correct spark plug part number and gap specification (typically 0.043" / 1.1mm for this engine)

Procedure

1. 1

   Remove engine cover
   Grasp the engine cover firmly and pull upward to disengage the retaining clips. The cover is held by push-clips only and does not require tools to remove. Set aside in a clean area.
2. 2

   Disconnect ignition coil electrical connectors
   Locate all four ignition coils on top of the valve cover. Press the locking tab on each coil connector and pull straight up to disconnect. Do not pull on the wiring harness itself.
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 unless coils are being replaced.
4. 4

   Extract ignition coils
   Grasp each ignition coil firmly and pull straight up with a gentle twisting motion. The coil boots may stick to the spark plugs due to heat cycling. If resistance is encountered, twist gently while pulling to break the seal. Inspect coil boots for cracks, oil contamination, or carbon tracking.
   ⚠If oil is present in spark plug wells, a valve cover gasket leak exists and should be addressed before completing this procedure.
5. 5

   Clean spark plug wells
   Use compressed air or a clean lint-free cloth to remove any debris from around the spark plugs and inside the plug wells. Debris falling into the cylinder can cause engine damage.
6. 6

   Remove spark plugs
   Using a 5/8" (16mm) spark plug socket with extension, carefully unscrew each spark plug. Turn counterclockwise and maintain straight alignment to avoid cross-threading. Inspect removed plugs for abnormal wear, oil fouling, or carbon buildup which may indicate engine issues.
7. 7

   Prepare new spark plugs
   Verify each new spark plug gap using a gap tool; factory gaps may not match specification. Adjust to 0.043" (1.1mm) if needed by gently bending the ground electrode. Apply a small amount of anti-seize compound to the threads, avoiding the electrode area. Use sparingly as excess can cause fouling.
8. 8

   Install new spark plugs
   Thread each spark plug by hand into the cylinder head, turning clockwise. Ensure plugs thread smoothly without resistance. If resistance is felt, remove and restart to prevent cross-threading. Once hand-tight, use torque wrench to tighten to specification.
   Torque spec

   Spark Plug19 Nm (14 lb-ft)
9. 9

   Prepare ignition coils for installation
   Apply a thin coat of dielectric grease to the inside of each coil boot where it contacts the spark plug terminal. This prevents moisture intrusion and aids future removal. Inspect coil boots for any damage or deterioration.
10. 10

    Install ignition coils
    Align each ignition coil with its corresponding spark plug and push down firmly until the coil seats completely on the valve cover. The boot must fully engage with the spark plug terminal. Install and hand-tighten the retaining bolt for each coil.
11. 11

    Torque ignition coil bolts
    Using a torque wrench with 10mm socket, tighten each ignition coil bolt to specification. Tighten in a crossing pattern (cylinders 1-4-2-3) for even seating.
    Torque spec

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

    Reconnect electrical connectors
    Push each ignition coil electrical connector onto its respective coil until the locking tab clicks into place. Gently tug on each connector to verify secure engagement.
13. 13

    Reinstall engine cover
    Align the engine cover mounting points with the clips on the engine. Press down firmly at each clip location until you hear/feel them snap into place. Ensure cover is fully seated and secure.

Reassembly

1. Reconnect negative battery terminal and tighten securely
2. Verify all electrical connectors are fully engaged and locked
3. Ensure no tools or parts remain in engine compartment

Verification

• Start engine and verify it runs smoothly without misfires or rough idle
• Check for any unusual noises, vibrations, or check engine light
• Allow engine to reach operating temperature and verify smooth operation
• Perform a test drive to confirm proper acceleration and no hesitation under load
• Scan for diagnostic trouble codes if check engine light illuminates

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