Mazda RX-8: Renesis Leading & Trailing Ignition Coil Failure

The 13B-MSP Renesis uses a twin-plug ignition system with separate leading and trailing ignition coils for each rotor, producing four coils in total. The trailing coils, which fire at higher voltages to ignite the charge at a different rotor face position, fail at elevated rates due to heat stress and voltage fatigue in the tight engine bay environment. Coil failure causes single-rotor misfires, hard starting, and dramatically increases the risk of engine flooding as unburned fuel enters the exhaust stream. Prolonged misfires destroy the catalytic converter. Mazda issued a technical service bulletin addressing premature coil failure on early Series 1 vehicles, and replacement of all four coils as a complete set is standard practice.

• Engine misfire especially noticeable under light throttle loads
• Hard start or extended cranking before the engine fires
• Rough idle that partially clears at higher RPM
• Check engine light with ignition misfire codes P0300 through P0304
• Increased engine flooding risk following misfire events
• Loss of power attributed to one rotor not contributing evenly

1. 1

   Inspect all four ignition coil bodies for cracking, heat discolouration, or carbon tracking on the boot contacts.

2. 2

   Test coil primary and secondary resistance against Mazda specifications.

3. 3

   Confirm when the coils were last replaced and whether all four were replaced simultaneously as recommended.

4. 4

   If a workshop inspection is possible: OBD-II scan for active or stored ignition misfire codes.

Parts involved: Ignition coil.

$400 to $1,400 at New Zealand independent workshop rates. That is for this job on its own, not for the car.

An estimate, in NZD, for the repair as normally carried out. What a specific car costs depends on which part has failed and what it damaged on the way — treat this as the floor for a negotiation, not a quote.

• “When were the ignition coils last replaced and were all four done at once?”
• “Has the car ever had ignition misfire codes or a misfire diagnosis?”
• “What spark plugs are currently fitted and when were they last changed?”
• “Has the car ever been recovered from an engine flooding no-start event?”

The failure described above is documented in published sources — owner forums, technical service bulletins, recall notices and workshop write-ups — held in our fault database. The inspection instructions and the cost estimate are KickTyres’ own interpretation of them, and it is a starting point for an inspection rather than a manufacturer statement.