Replace spark plugs on a 2015 Kia Forte 1.8L I4 engine to restore optimal ignition performance and fuel efficiency.

Warnings

Tools required

Parts

• Spark plugs (iridium or platinum) × 4 — Use OEM specification NGK or equivalent

Preparation

1. Ensure engine is completely cool to the touch
2. Park vehicle on level surface and engage parking brake
3. Open hood and secure with prop rod
4. Disconnect negative battery terminal to prevent accidental starter engagement
5. Remove engine cover by releasing clips and removing fasteners

Procedure

1. 1

   Remove engine cover
   Carefully release the plastic clips holding the engine cover by pulling upward. Remove any remaining fasteners using a 10mm socket. Lift the engine cover away to expose the ignition coils.
   Torque spec

   Engine Cover Clips3 Nm (2 lb-ft)
2. 2

   Disconnect ignition coil connectors
   Locate all four ignition coils on top of the engine. Press the release tab on each electrical connector and pull straight up to disconnect. Note the cylinder numbering (1-4 from left to right when facing the engine) for proper reassembly.
   ℹ️Mark or photograph coil positions if connectors are not clearly labeled
3. 3

   Remove ignition coils
   Using a 10mm socket, remove the single bolt securing each ignition coil. Carefully pull each coil straight up with a slight twisting motion to break the seal. Inspect coil boots for cracks or damage and replace if necessary.
   Torque spec

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

   Clean spark plug wells
   Use compressed air or a clean rag to remove any debris, dirt, or oil from around the spark plug wells. This prevents contamination from falling into the cylinders when plugs are removed.
   ⚠If oil is present in spark plug wells, valve cover gasket replacement may be needed
5. 5

   Remove old spark plugs
   Using a spark plug socket with extension, carefully loosen each spark plug by turning counterclockwise. Once loose, unthread by hand to prevent cross-threading. Remove all four plugs and inspect electrodes and insulators for wear, carbon buildup, or abnormal deposits.
   ℹ️Inspect removed plugs for unusual wear patterns that may indicate engine problems
6. 6

   Gap and prepare new spark plugs
   Check the gap on each new spark plug using a gap tool (typically 0.039-0.043 inches or 1.0-1.1mm for this engine; verify with plug manufacturer). Apply a small amount of anti-seize compound to the threads of each plug, avoiding the electrode area.
   ⚠Do not apply anti-seize to electrode or insulator; keep compound on threads only
   Torque spec

   Spark Plug19 Nm (14 lb-ft)
7. 7

   Install new spark plugs
   Carefully thread each new spark plug by hand into the cylinder head, ensuring it starts smoothly without resistance. Once hand-tight, use the torque wrench and spark plug socket to tighten to specification. Install all four plugs.
   ⚠️If plug does not thread easily by hand, stop and check for cross-threading; forcing a cross-threaded plug will destroy cylinder head threads
   Torque spec

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

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

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

   Reconnect electrical connectors
   Reconnect the electrical connector to each ignition coil, ensuring each clicks firmly into place. Verify all connections are secure by gently tugging on each connector.
   ℹ️Ensure connectors are fully seated to prevent misfires
10. 10

    Reinstall engine cover
    Position the engine cover back onto the engine. Press down firmly on clip locations to secure, then install any remaining fasteners. Reconnect the negative battery terminal.
    Torque spec

    Engine Cover Clips3 Nm (2 lb-ft)

Reassembly

1. Ensure all electrical connectors are fully seated and locked
2. Verify engine cover is properly secured at all mounting points
3. Reconnect negative battery terminal and tighten securely

Verification

• Start engine and listen for smooth, even idle with no misfires or unusual sounds
• Check for any diagnostic trouble codes using an OBD-II scanner
• Verify no spark plug warning lights on instrument cluster
• Test drive vehicle and confirm smooth acceleration with no hesitation or misfires under load
• Visually inspect engine cover area for proper installation and no loose components

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