Parts for your 2018 Toyota Mark x-Ignition coils

2018 Toyota Mark X ignition coils — what they do and when to replace them

Technical sources including the Toyota Repair Manual for the Mark X GRX130 series (2016–2019), the Toyota Electronic Parts Catalogue, and Denso ignition system documentation for the 4GR‑FSE and 2GR‑FSE engines confirm that the 2018 Toyota Mark X uses a coil‑on‑plug setup. That means six individual ignition coils, one perched on each spark plug on the V6. No distributor, no single “coil pack” — just compact coils delivering a hot, precisely timed spark.

Those coils take the 12 volts from the battery and step it up to tens of thousands of volts, firing the plugs cleanly under all conditions. On the direct‑injection GR‑series engines, reliable spark is crucial for crisp starts, smooth idle, lean cruise, and decent fuel economy.

Ignition coils aren’t a scheduled replacement item on the Mark X, they’re replaced as needed. As part of routine servicing, it’s smart to inspect the coils any time the engine covers are off — usually when changing spark plugs (about every 100,000 km with the specified iridium plugs). Check for heat‑cracked boots, tracking marks, oil in the plug tubes (a rocker cover seal issue), or loose connectors. If a misfire pops up, scan for codes like P030x (cylinder‑specific misfire) or P035x (coil circuit). A handy diagnosis tip is to swap the suspected coil to another cylinder and see if the fault follows.

• Common symptoms: rough idle, hesitation under load, higher fuel use, sulphur/“raw fuel” smell, and the MIL on.
• Best practice: stick with OE‑quality coils (Denso is the factory supplier), keep the coil boots clean and dry, and use a light smear of dielectric grease inside the boot if needed — never on the electrical terminals.

Replacement is straightforward: remove the engine cover, unplug the connector, undo the single coil bolt, and lift the coil straight up. Refit carefully and tighten to the factory torque spec from the Toyota manual, don’t overdo it as the bolts thread into alloy. If one coil fails at higher kilometres (say 150–200k), some owners choose to replace the set, but it’s not mandatory if the others test fine. Lastly, healthy battery voltage and the correct spec plugs help coils live a long, drama‑free life in Australian and New Zealand conditions.

Popular questions about 2018 Toyota Mark X ignition coils

Does the 2018 Mark X use individual coils or a single coil pack?
The 2018 Mark X (GRX130) uses six individual coil‑on‑plug ignition coils — one per cylinder — on both the 2.5‑litre 4GR‑FSE and 3.5‑litre 2GR‑FSE V6 engines. This is confirmed by Toyota’s service literature and parts catalogues.

How often should ignition coils be replaced?
There’s no fixed interval. Coils are replaced when faulty. Inspect them during spark plug changes (around 100,000 km) and any time there’s a misfire. Many last well past 150,000 km, replace only the bad unit unless there’s a pattern of failures.

What’s the best coil brand for a Mark X?
Denso is the OE supplier for the GR‑series engines. OE or OE‑equivalent coils generally fit and perform correctly. If unsure, match by VIN using a Toyota parts catalogue to ensure the right coil for the specific engine variant.