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RX-8 · Reliability

RX-8 Ignition coils + spark plugs

Your RX-8

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Restores lost power
Easy$150–$3501.5–2.5 hrs
All RX-8 mods

Why do it

Worn coils and plugs are one of the most common causes of misfires and hard starts on the RX-8. Many owners replace them first, before any other mod.

Tools you'll need

Parts to buy

Always double-check fitment for your exact year, trim and transmission before buying. Prices change. ModBuddy doesn't earn money from these links.

Before you start

  • Buy the full set: 4 coils, 2 leading plugs (NGK RE7C-L), 2 trailing plugs (NGK RE9B-T), and ideally a new wire set. RX-8 ignition parts wear together, so replace them as a set.
  • Work on a fully cold engine.
  • Have a 13/16" spark plug socket. That's the hex size on the NGK RX-8 plugs.

Video guide

Coil, spark plug and wire replacement (Series 1 RX-8)
by boredmder on YouTube

Uses the same NGK plugs and wires we list. He removes the airbox only so the camera can see; you usually don't need to. Each ▶ button below jumps to that step in the video.

Watch the whole video

Steps

  1. Disconnect the battery

    • Lift the battery cover and disconnect the negative terminal so nothing can spark while you work.

  2. Photograph everything

    • Take clear photos of how the coils, wires and connectors are routed before you unplug anything.
    • The plug wires are different lengths and go to specific plugs, so the photos save you from mixing them up.

  3. Get access to the plugs

    • The plugs sit low on the engine. Many owners raise the front of the car on jack stands and remove the wheel and inner splash shield on the plug side for easier reach.
    • Use your service manual for the exact access route on your year.
    Watch this step (6:27–7:51)

  4. Swap the plugs one at a time

    • Remove one wire, remove that plug, and install the new one in the same hole before moving to the next.
    • Leading plugs (RE7C-L) and trailing plugs (RE9B-T) are different. Check each old plug's part number as it comes out and replace it with the matching new one.

    Tip: NGK's method for these gasket-seat plugs: thread the plug in by hand until the gasket touches, then turn it 1/2 to 2/3 more with the socket. Or use the torque spec in your service manual. Never force a plug that won't thread by hand.

    Watch this step (7:51–13:25)

  5. Replace the coils

    • Unplug and unbolt one coil at a time and fit the new one in the same spot.
    • The RX-8 uses 4 coils for its twin-spark system, so all 4 get replaced.
    Watch this step (2:41–6:27)

  6. Fit the new wires

    • Replace wires one at a time, matching each new wire to the old one by length.
    • Push each boot on until you feel it click onto the plug or coil terminal.
    Watch this step (13:25–15:45)

  7. Reassemble and test

    • Reinstall any splash shields and wheels, torquing the wheel nuts to spec.
    • Reconnect the battery, start the engine and let it idle. It should be smooth with no flashing check-engine light.

How to know it worked

Safety first

  • Park on flat, solid ground, set the parking brake and chock the wheels.
  • Use jack stands rated for your car. Never get under a car held up only by a jack.
  • Let the engine and exhaust cool completely before touching them.
  • Disconnect the negative battery terminal before unplugging sensors or electrical parts.
  • Wear safety glasses, and gloves around sharp heat shields and hot fluids.
  • Tighten bolts to the torque spec in your factory service manual.
  • If a step doesn't match your car or you're unsure, stop and ask a shop.

These are overview steps written to help you plan the job. Always follow the instructions that come with your part and the procedures and torque specs in your factory service manual. Horsepower is an estimate; results vary.