Replace spark plugs on a 2016-2024 Hyundai Tucson 2.5L I4 engine to restore ignition performance and fuel efficiency.

Warnings

Tools required

Parts

• Spark plugs (Iridium or Platinum) × 4 — Hyundai 18855-10080 or NGK equivalent

Preparation

1. Ensure engine is completely cool to the touch.
2. Park vehicle on level ground and engage parking brake.
3. Disconnect negative battery terminal to prevent accidental ignition system activation.
4. Gather all tools and new spark plugs before beginning.

Procedure

1. 1

   Remove engine cover
   Remove the plastic engine cover by pulling upward on the clips or removing fasteners. Some models use twist-lock clips while others use screws. Store the cover and hardware in a safe location.
   Torque spec

   Cover Screws11 Nm (8 lb-ft)

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

   Disconnect ignition coil connectors
   Locate all four ignition coils on top of the valve cover. Press the locking tab on each coil electrical connector and pull straight up to disconnect. Mark or remember the cylinder order if connectors are not identical.
   ℹ️Connectors may be stiff; wiggle gently while pulling to avoid breaking the locking tab.
3. 3

   Remove ignition coil bolts
   Using a 10mm socket, remove the single bolt securing each ignition coil to the valve cover. Keep bolts organized by cylinder position.
   Torque spec

   Ignition Coil Bolt11 Nm (8 lb-ft)
4. 4

   Extract ignition coils
   Grasp each ignition coil firmly and pull straight upward with a twisting motion to break the seal. The coil extends down into the spark plug well. Inspect the coil boot for damage, cracks, or oil contamination.
   ⚠If oil is present in spark plug wells, valve cover gaskets may need replacement. Address this issue to prevent future ignition problems.
5. 5

   Clean spark plug wells
   Use compressed air or a vacuum to remove any debris, dirt, or oil from the spark plug wells. This prevents contamination from falling into the combustion chamber when plugs are removed.
   ⚠Never allow debris to enter the cylinder. Cover open wells with clean rags if interrupting work.
6. 6

   Remove old spark plugs
   Using a spark plug socket with extension, carefully loosen each spark plug by turning counterclockwise. Once loose, unscrew by hand and remove from the well. Inspect old plugs for wear patterns, fouling, or damage to assess engine condition.
   Torque spec

   Spark Plug20 Nm (15 lb-ft)
7. 7

   Gap and prepare new spark plugs
   Check and adjust the gap on each new spark plug to the specification listed in your owner's manual (typically 0.039-0.043 inches for this engine). Apply a small amount of anti-seize compound to the threads of each plug, avoiding the electrode area.
   ⚠Use anti-seize sparingly. Excess compound can contaminate the electrode or cause inaccurate torque readings.
   Torque spec

   Spark Plug20 Nm (15 lb-ft)
8. 8

   Install new spark plugs
   Thread each new spark plug into the cylinder head by hand, turning clockwise until finger-tight. This ensures proper thread alignment and prevents cross-threading. Use the spark plug socket and torque wrench to tighten to specification.
   ⚠️Cross-threading will destroy aluminum cylinder head threads. If plug does not thread smoothly by hand, remove and restart.
   Torque spec

   Spark Plug20 Nm (15 lb-ft)
9. 9

   Apply dielectric grease to coil boots
   Apply a small amount of dielectric grease inside each ignition coil boot. This prevents moisture intrusion, eases future removal, and ensures good electrical contact.
   ℹ️Dielectric grease is non-conductive and prevents arcing. Do not substitute with regular grease.
10. 10

    Reinstall ignition coils
    Insert each ignition coil straight down into its spark plug well, ensuring it seats fully onto the spark plug. Push down firmly until you feel the coil bottom out on the plug.
    Torque spec

    Ignition Coil Bolt11 Nm (8 lb-ft)
11. 11

    Secure ignition coils
    Install and torque the ignition coil bolt for each cylinder to specification using a torque wrench and 10mm socket.
    Torque spec

    Ignition Coil Bolt11 Nm (8 lb-ft)
12. 12

    Reconnect electrical connectors
    Push each ignition coil electrical connector onto its respective coil until you hear or feel a positive click. Gently tug on each connector to verify it is locked in place.
13. 13

    Reinstall engine cover
    Position the engine cover and secure with clips or screws. Ensure all fasteners are properly engaged and torqued to specification if applicable.
    Torque spec

    Cover Screws11 Nm (8 lb-ft)

    Engine Cover Clips3 Nm (2 lb-ft)
14. 14

    Reconnect battery and test
    Reconnect the negative battery terminal. Start the engine and verify smooth operation with no misfires, unusual noises, or warning lights.

Reassembly

1. Ensure all electrical connectors are fully seated and locked.
2. Verify engine cover is properly secured and all clips/screws are installed.
3. Double-check that no tools or parts were left in the engine bay.

Verification

• Start the engine and listen for smooth, even running with no misfires or rough idle.
• Verify no check engine light or misfire codes are present using an OBD-II scanner if available.
• Allow engine to reach operating temperature and confirm smooth acceleration with no hesitation.
• Visually inspect for any disconnected wires or improperly seated ignition coils.

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