Toyota Mark X: Ignition coil failure causing misfire and stalling

The Mark X runs a coil directly on each spark plug, and they fail with age and underbonnet heat rather than mileage — which matters on a Japanese import that may have sat before shipping. A failing coil misfires under load first, then at idle, and can stall the car outright. Left running on a dead cylinder, unburnt fuel passes into the exhaust and can damage the catalytic converter, which turns a modest job into an expensive one. Coils are individually replaceable and not costly; owners commonly change the full set on a high-kilometre car and be done with it.

• Engine shaking or juddering, worst under acceleration
• Flashing engine warning light — that flashing specifically means an active misfire
• Unstable idle, sometimes stalling at a standstill
• Hard starting despite a healthy battery and starter

Start it cold and let it idle for a couple of minutes with your hand resting on the gear lever or centre console — a misfire comes through as a rhythmic shake you can feel as much as hear. On the test drive, accelerate hard in a mid gear up a hill, which loads the ignition and is where a weak coil shows first, and watch the dash: an engine light that FLASHES rather than glowing steadily means the car is misfiring right now and you should stop driving it. Listen at the exhaust for an uneven beat. Under the bonnet with the engine off, look at the coils on top of each cylinder head for cracked plastic or corrosion at the connectors. Ask when the plugs and coils were last done. If a workshop inspection is possible: a scan tool reads misfire counts per cylinder and identifies the exact coil, which no road test can do.

Parts involved: Ignition coil.

$250 to $1,200 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 spark plugs and ignition coils last replaced?”
• “Has the engine light ever come on, and was it flashing?”
• “Does it ever shake or stumble when you accelerate?”

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.