Parts for your 2010 Subaru Impreza-Ignition leads

2010 Subaru Impreza ignition leads — do they apply, and what to service

Whether a 2010 Subaru Impreza has ignition leads depends on the engine fitted. Technical references including the Subaru Factory Service Manual for the GE/GH/GV series (Engine/ME – Ignition System) and the Subaru Electronic Parts Catalogue (FAST) show two distinct setups for this model year. Non‑turbo variants such as the 2.5i with the EJ253 engine use a four‑post coil pack with high‑tension ignition leads (spark plug cords). Turbo models (WRX/STI using EJ255/EJ257) and several 2.0‑litre variants use coil‑on‑plug ignition, where a coil sits directly on each spark plug, so there are no traditional ignition leads. This means ignition leads are relevant for 2010 Impreza models with the EJ253 and similar coil‑pack layouts, but not used on WRX/STI and other coil‑on‑plug engines.

For vehicles that do have them, ignition leads carry high voltage from the coil pack to each spark plug. Their job is simple but crucial: deliver a strong, clean spark at the right time so the boxer engine starts crisply, idles smoothly, and pulls cleanly under load. Age, heat, oil contamination, and flexing can break down the insulation or increase resistance, leading to misfires, rough running, poor fuel economy, and hard starting.

Servicing wise, they’re a tidy, affordable win. Most workshops in Australia and New Zealand will inspect leads at each service, and many recommend replacement somewhere around 100,000–150,000 km, or sooner if there are misfire symptoms. It’s smart to replace them when fitting new spark plugs to keep the whole ignition path fresh. Use OEM or high‑quality aftermarket leads with the correct resistance spec for the EJ engine, and match lengths/cylinder routing as per the factory guide.

• Common signs they’re due: intermittent misfire (especially in the wet), visible cracking or swelling, white tracking marks, a ticking/arching sound, or a check engine light with random/multiple misfire codes.
• Simple care tips: keep oil out of the plug wells, avoid yanking on the cable (twist the boot instead), and use a dab of dielectric grease inside the boots for easier future removal and better sealing.

1. Replace one lead at a time to avoid mixing up cylinder order.
2. Push boots on firmly until you feel the click at the plug and coil pack.
3. Clip leads into the factory retainers so they don’t chafe on brackets or the manifold.

If the car is a 2010 WRX or STI (or any coil‑on‑plug variant), there are no ignition leads to service. Instead, each cylinder has its own coil, faults there are addressed by testing or replacing the individual coil packs per the Subaru Service Manual.

Which 2010 Impreza models actually have ignition leads?

Most non‑turbo 2010 Imprezas with the EJ253 engine use a single coil pack and four high‑tension leads. WRX/STI models (EJ255/EJ257) use coil‑on‑plug, so there are no traditional leads. The Subaru Factory Service Manual and Parts Catalogue outline these setups by engine code and VIN.

How often should ignition leads be replaced on a 2010 Impreza?

There’s no hard expiry, but many techs suggest inspecting at every service and replacing around 100,000–150,000 km, or any time there are misfires, cracking, or high resistance readings. It’s common to fit new leads when doing spark plugs to keep the ignition system in top nick.

What are the symptoms of failing ignition leads?

Look for rough idle, hesitation under load, worse fuel economy, harder cold starts, a ticking/arching noise, or a check engine light with P0300–P0304 codes. Wet weather often makes weak leads show up. Visual cracks or white tracking marks on the insulation are a giveaway.