How to Replace Ignition Coils on a 2018 Hyundai Elantra (Fix Misfire & Rough Idle)
Step-by-step coil-on-plug replacement with tools, parts list, torque specs (9.8 Nm), and code-clearing tips for 2015, 2016, 2017, 2018, 2019, 2020
How to Replace Ignition Coils on a 2018 Hyundai Elantra (Fix Misfire & Rough Idle)
Step-by-step coil-on-plug replacement with tools, parts list, torque specs (9.8 Nm), and code-clearing tips for 2015, 2016, 2017, 2018, 2019, 2020
đź”§ Elantra - Ignition Coil Replacement
Your Elantra uses coil-on-plug ignition coils (one coil per cylinder) mounted on top of the engine. Replacing a bad coil can fix misfires, rough idle, and a flashing check engine light.
Difficulty Level: Beginner | Estimated Time: 0.5-1.5 hours
⚠️ Safety & Precautions
- ⚠️ Let the engine cool fully before starting.
- ⚠️ Keep the key away from the car to prevent accidental electrical wake-up.
- ⚠️ If you disconnect the battery, you may lose radio presets.
- ⚠️ Do not pull on wiring—only pull on connectors.
đź”§ Required Tools
You'll need the following tools for this repair:
- 10mm socket
- 1/4" drive ratchet
- 3" socket extension
- Torque wrench (5-30 Nm range)
- Trim clip tool
- Small flathead screwdriver
- OBD2 scan tool (basic code reader)
- Nitrile gloves
- Safety glasses
🔩 Required Parts
HowToo sells all the parts you need for this repair:
- Ignition coil - Qty: 1-4
- Dielectric grease - Qty: 1
đź“‹ Before You Begin
- Park on level ground, shift to Park, and set the parking brake.
- Open the hood and let the engine cool.
- If you want maximum safety around connectors, disconnect the battery negative terminal using a 10mm socket.
🔨 Step-by-Step Instructions
Follow these steps in order:
Step 1: Remove the engine cover (if equipped)
- Grip the cover and pull straight up to release the rubber grommets.
- If any clips resist, use a trim clip tool to lift gently.
- Pull up evenly—don’t yank one corner.
Step 2: Locate the ignition coils
- The coils are the 4 identical units on top of the valve cover, each with an electrical connector.
Step 3: Unplug the coil electrical connector
- Press the connector lock tab and pull the connector straight off.
- If the tab is stubborn, use a small flathead screwdriver to gently lift the lock while pulling.
- Never pry hard on the plastic tab.
Step 4: Remove the ignition coil hold-down bolt
- Use a 10mm socket, 3" socket extension, and 1/4" drive ratchet to remove the bolt.
- Set the bolt aside where it won’t fall into the engine bay.
Step 5: Remove the ignition coil
- Twist the coil slightly left-right to break the seal, then pull straight up.
- If it’s tight, keep twisting while pulling—do not use tools to pry under it.
Step 6: Install the new ignition coil
- Put a tiny smear of dielectric grease inside the rubber boot (this helps prevent moisture and makes future removal easier).
- Push the coil straight down until it fully seats on the spark plug.
Step 7: Reinstall and torque the coil bolt
- Start the bolt by hand to avoid cross-threading.
- Tighten using a torque wrench (5-30 Nm range): Torque to 9.8 Nm (7 ft-lbs)
Step 8: Reconnect the coil connector and repeat
- Push the connector on until it clicks.
- Repeat Steps 3–7 for any other coils you’re replacing.
Step 9: Reinstall the engine cover
- Align the cover over the grommets and press down firmly with your hands.
âś… After Repair
- Reconnect the battery (if disconnected) using a 10mm socket.
- Use an OBD2 scan tool to clear any misfire codes.
- Start the engine and listen for a smooth idle.
- Test drive 10–15 minutes and confirm the check engine light stays off.
- If the light flashes or the engine still misfires, stop driving and scan again.
đź’° DIY vs Shop Cost
Shop Cost: $200-$500 (parts + labor, depending on how many coils)
DIY Cost: $35-$300 (parts only, 1 vs all 4)
You Save: $100-$250 by doing it yourself!
Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 0.5-1.0 hours.
🎯 Ready to get started?
HowToo makes it easy: same-day/2-day shipping on every part, plus all the tools and specialty tools you need! Check out the parts and tools sections below to add everything to your cart.


















