Parts for your 2018 Mazda 3-Ignition coils

2018 Mazda 3 ignition coils

Ignition coils absolutely apply to the 2018 Mazda 3. Technical references including the Mazda Workshop Manual for the BN-series Mazda 3 (Ignition System — SKYACTIV‑G 2.0/2.5), Mazda’s Electronic Parts Catalogue for the 2018 BN, and DENSO’s aftermarket application data all specify a coil‑on‑plug ignition system on the 2.0L and 2.5L SKYACTIV‑G petrol engines. That means there’s one ignition coil per cylinder under the bonnet, mounted directly on each spark plug.

The job of the ignition coil is to transform the vehicle’s 12 volts into the tens of thousands of volts needed to jump the spark plug gap. With coil‑on‑plug, each cylinder gets a dedicated coil for precise timing and a strong, clean spark. This setup helps the Mazda 3 deliver crisp throttle response, good fuel economy, and reliable cold starts across Aussie and Kiwi conditions.

Ignition coils aren’t a scheduled replacement item on the 2018 Mazda 3, they’re typically replaced only if they fail testing or show damage. However, they’re right on top of the spark plugs, so it’s smart to inspect them whenever the iridium plugs are changed (often around 120,000 km, per Mazda service guidance). At that time, check for heat‑hardened or cracked boots, oil contamination from rocker cover seals, and any signs of carbon tracking. A light smear of dielectric grease on clean plug boots can help prevent future misfire paths and ease removal later on.

Common hints that a coil is on the way out include a rough idle, hesitation under load, increased fuel use, and a check engine light with a misfire code (P0300–P0304). A quick swap test of suspect coils between cylinders, combined with scan‑tool misfire counters, can confirm the culprit. When replacement is due, stick with quality parts (genuine Mazda or a reputable OE supplier) and follow factory torque specs for both spark plugs and coil hold‑downs. If one coil fails at high kilometres, some owners choose to replace the full set for peace of mind, but it’s not mandatory if the others test fine.

• Keep water out of the plug wells when washing the engine bay.
• Address any oil leaks promptly to protect the coil boots.
• Avoid harsh solvents on coils and boots, use appropriate cleaners only.

How many ignition coils does a 2018 Mazda 3 have?

The 2018 Mazda 3 uses a coil‑on‑plug design with one ignition coil per cylinder. On the common 2.0L and 2.5L SKYACTIV‑G petrol engines, that means four coils in total.

What are the common symptoms of a failing ignition coil?

Expect a rough idle, sluggish acceleration, higher fuel use, and a check engine light. Scan tools typically show misfire codes like P0300 to P0304. Under load, the car may feel like it’s stumbling, especially on hills or when overtaking.

Do ignition coils need replacing when changing spark plugs?

Not by default. Coils aren’t a routine service item. Replace them only if testing shows a fault or the boots are brittle, cracked, or oil‑soaked. During plug changes, inspect the coils, renew boots if needed, and use dielectric grease to protect the interface.