Parts for your 2014 Subaru Impreza-Ignition coils

2014 Subaru Impreza ignition coils — what they do and how to look after them

Ignition coils are absolutely relevant to the 2014 Subaru Impreza. The factory Service Manual available via Subaru’s Technical Information System (STIS) outlines a coil-on-plug ignition system on both the FB20 2.0-litre non‑turbo and the EJ turbo variants found in some markets. Major parts catalogues (Subaru EPC) and leading ignition suppliers (e.g., NGK, Denso) list four individual coil-on-plug units for this model year. That means there’s one ignition coil per cylinder mounted directly on the spark plug—no distributor, no shared coil pack.

On a 2014 Impreza, each coil’s job is to take the 12‑volt feed and step it up to the tens of thousands of volts needed to fire the spark plug at precisely the right moment. The engine control module triggers each coil on command, keeping combustion smooth, efficient, and clean. Because these are coil-on-plug units on a boxer engine, they sit outboard on each cylinder bank, so access is from the sides of the engine bay—often easier with the airbox or battery moved out of the way on one side.

Coils aren’t a regular “consumable” like oil or filters, but they do age with heat, vibration and moisture. As part of routine servicing, it’s smart to:

• Inspect coil connectors and wiring for looseness, corrosion, or broken tabs.
• Check for oil residue from rocker cover leaks that can contaminate coil boots.
• Replace spark plugs at the schedule (typically around 100,000 km for OE iridium) and assess coil boots for cracking at the same time.
• Avoid blasting the engine bay with high-pressure water—moisture ingress can shorten coil life.

Tell‑tale signs of a crook coil include a flashing check engine light, misfire codes (P0301–P0304), coil circuit codes (P0351–P0354), rough idle, hard starting, poor fuel use, or a noticeable stumble under load. If a single coil fails, replacing just that one is usually fine, on higher‑kilometre cars, many owners opt to swap the set to keep the engine’s behaviour even. Stick with OEM‑quality parts, seat the boot squarely on the plug, and clip the connector until it positively clicks. If using dielectric grease, keep it to a light smear inside the rubber boot only—never on the electrical pins.

Handled this way, the 2014 Impreza’s coils typically provide long, reliable service, helping the boxer engine run sweet as and sip fuel the way it should.

How long do ignition coils last on a 2014 Impreza?

There’s no fixed interval, but many see well over 150,000 km if heat and moisture are kept in check. They’re inspected during plug changes and replaced when symptoms or fault codes point to a failing unit.

Can a bad coil damage the catalytic converter?

Yes. A persistent misfire can send unburnt fuel into the exhaust and overheat the cat. If there’s a flashing check engine light or a clear misfire, it’s best to sort it promptly to protect the converter.

Should all four coils be replaced at once?

Not mandatory. Replacing the single failed coil is acceptable. On high‑kilometre cars, doing the full set can restore consistent performance and avoid repeat visits, especially if multiple coils test weak.