This procedure covers the removal and replacement of all four ignition coils on the 2014-2019 Toyota Corolla 1.8L I4 engine, including spark plug inspection and replacement.

Warnings

Tools required

Parts

• Ignition coil × 4 — 90919-02260 or equivalent
• Spark plug × 4 — 90919-01253 (Denso SK20R11) or equivalent

Preparation

1. Ensure engine is completely cool to the touch
2. Gather all tools and parts before beginning
3. Park vehicle on level surface and engage parking brake
4. Open hood and secure with prop rod

Procedure

1. 1

   Remove engine cover
   Grasp the engine cover firmly at the front center and pull straight up to release the retaining clips. The cover is secured by push-fit grommets and does not require tools. Set aside in a clean area.
2. 2

   Locate and identify ignition coils
   Identify all four ignition coils on top of the cylinder head. They are black cylindrical components with electrical connectors on top, numbered 1-4 from left to right (timing belt side to alternator side). Note the routing of the wiring harness.
3. 3

   Disconnect ignition coil electrical connectors
   Press down on the locking tab of each electrical connector while pulling straight up to disconnect. Start with cylinder 1 (leftmost) and work toward cylinder 4. Do not pull on the wires themselves.
4. 4

   Remove ignition coil mounting bolts
   Using a 10mm socket, remove the single bolt securing each ignition coil. Keep bolts organized by cylinder number if reusing. Each coil has one bolt at the top center of the coil body.
   Torque spec

   Ignition Coil Bolts8 Nm (6 lb-ft)
5. 5

   Extract ignition coils from cylinder head
   Grasp each coil firmly and gently twist approximately 1/4 turn in each direction to break the seal on the rubber boot. Pull straight up with steady pressure. If resistance is felt, continue gentle twisting while pulling. Do not pry or force the coils out.
   ⚠Excessive force can tear the coil boot inside the spark plug well, requiring difficult removal of boot remnants
6. 6

   Clean spark plug wells
   Use compressed air or a shop vacuum to remove any debris, dirt, or oil from around each spark plug before removal. This prevents contamination from falling into the combustion chamber. Inspect for oil accumulation which may indicate valve cover gasket leakage.
7. 7

   Remove spark plugs
   Using a 5/8-inch (16mm) spark plug socket with extension, carefully unthread each spark plug. Turn counterclockwise with steady pressure. Once loose, remove by hand if possible to prevent dropping. Keep plugs organized by cylinder number for inspection.
   Torque spec

   Spark Plugs - Aluminum Head20 Nm (15 lb-ft)
8. 8

   Inspect old spark plugs
   Examine each spark plug for wear, fouling, or damage. Check electrode gap and condition of the insulator. Normal plugs should have light tan to gray deposits. Heavy carbon buildup, oil fouling, or electrode erosion indicates potential engine issues that should be addressed.
9. 9

   Prepare and gap new spark plugs
   Verify new spark plugs are gapped to 1.1mm (0.043 inches) specification. Apply a small amount of anti-seize compound to the threads, avoiding the electrode end. Use sparingly; only the first 2-3 threads need coating.
   ⚠Excessive anti-seize can contaminate the spark plug and cause misfires; use only a thin coating on threads
10. 10

    Install new spark plugs
    Thread each new spark plug by hand into the cylinder head to prevent cross-threading. Once finger-tight, use the torque wrench and spark plug socket to tighten to specification. Work carefully to avoid damage to the aluminum threads.
    ⚠️Over-torquing spark plugs in aluminum heads can strip threads and require expensive head repair; use torque wrench and do not exceed specification
    Torque spec

    Spark Plugs - Aluminum Head20 Nm (15 lb-ft)
11. 11

    Inspect new ignition coils
    Check that new ignition coils match the originals in design and connector type. Inspect the rubber boot inside each coil for proper seating and condition. Apply a small amount of dielectric grease inside each boot to aid in future removal and prevent moisture intrusion.
12. 12

    Install new ignition coils
    Insert each ignition coil into its spark plug well, ensuring the boot fully seats onto the spark plug insulator. Push down firmly until the coil mounting hole aligns with the threaded hole in the valve cover. You should feel the boot click onto the spark plug.
13. 13

    Secure ignition coils with mounting bolts
    Install the mounting bolt for each coil and tighten to specification using a torque wrench. Do not over-tighten as this can crack the coil housing. Ensure each coil sits flush against the valve cover before final tightening.
    Torque spec

    Ignition Coil Bolts8 Nm (6 lb-ft)
14. 14

    Reconnect electrical connectors
    Press each electrical connector onto its corresponding ignition coil until you hear and feel a distinct click. Gently tug on each connector to verify it is fully locked in place. Ensure no wires are pinched or under tension.
15. 15

    Reinstall engine cover
    Align the engine cover grommets with their mounting posts on the engine. Press down firmly at each grommet location until the cover clicks into place and sits flush.

Reassembly

1. Double-check that all four electrical connectors are fully seated and locked
2. Verify engine cover is properly secured at all mounting points
3. Ensure no tools or parts have been left in the engine bay

Verification

• Start the engine and verify it runs smoothly without misfires or rough idle
• Check that the check engine light does not illuminate during initial startup
• Listen for any unusual noises or arcing sounds that might indicate improper coil seating
• Allow engine to reach operating temperature and confirm smooth acceleration with no hesitation
• Use an OBD-II scanner to verify no misfire codes (P0300-P0304) are present if available

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