Parts for your 2009 Subaru Impreza-Ignition coils

2009 Subaru Impreza Ignition Coils

Ignition coils are absolutely fitted to the 2009 Subaru Impreza. Technical references such as the Subaru Factory Service Manual for the GE/GH/GR series, Subaru’s FAST electronic parts catalogue, and major ignition component application data from OEM suppliers (e.g., Denso, NGK) all confirm that this model uses ignition coils. Turbocharged variants (WRX/STI with EJ255/EJ257) use coil-on-plug units at each cylinder, while many naturally aspirated models (EJ20/EJ253 in some markets) use a central coil pack feeding spark plug leads, or in some late builds, individual coils. Either way, coils are essential to the Impreza’s spark ignition system.

What do they do? The coil steps up the battery’s 12 volts to the high voltage needed to jump the plug gap and ignite the air–fuel mix. Healthy coils mean crisp starts, smooth idle, solid power, and good fuel economy. Tired coils can show up as hard starting, rough idle, hesitation under load, higher fuel use, and the check-engine light with misfire codes (P0300–P0304 or coil circuit codes P0351–P0354).

Servicing advice for a 2009 Impreza is straightforward. Coils aren’t a scheduled replacement item, but they should be inspected whenever spark plugs are changed (typically every 100,000 km for iridium plugs) or if any misfire is suspected. On coil-on-plug setups, check each coil’s boot for oil contamination from rocker cover leaks, heat cracking, or carbon tracking. On coil-pack setups, inspect the plug leads for brittleness or arcing and ensure secure connections. A light smear of dielectric grease inside boots helps repel moisture.

Diagnosis is easiest with a scan tool and a simple swap test: move a suspect coil to another cylinder and see if the misfire follows. Because modern coils are solid-state, resistance tests are of limited value. When replacing, choose quality OEM-equivalent parts from reputable brands, seat the boots cleanly on the plugs, and tighten mounting bolts and plugs to factory spec. In higher-kilometre cars, it’s fine to replace only the failed coil, though many owners of turbo models opt to refresh the full set due to heat stress. Keeping coils dry, addressing cam cover leaks promptly, and maintaining good plugs will help the ignition system go the distance.

• Common symptoms: rough idle, stumble under load, poor economy, CEL with misfire codes
• Good practice: inspect coils and boots at every plug change, fix oil leaks early
• Parts choice: stick with OEM-quality coils for reliable spark and longevity

Popular questions about 2009 Subaru Impreza ignition coils

Does my 2009 Impreza have coil-on-plug or a single coil pack?

It depends on the engine. WRX and STI models use individual coil-on-plug units on each cylinder. Many naturally aspirated EJ20/EJ253 models in this generation use a central coil pack with plug leads, though some late-production NA cars moved to individual coils. Checking the engine code and a quick visual under the covers will confirm which you have.

How often should the ignition coils be replaced?

There’s no fixed interval. Coils are replaced on condition—when misfires or related fault codes appear. As a rule of thumb, inspect them whenever you change spark plugs (about every 100,000 km for iridium). High-heat turbo cars may see shorter coil life than non-turbo models.

Can driving with a faulty coil damage other components?

Yes. Persistent misfires can overheat and damage the catalytic converter and may stress the ignition system and engine mounts. If a misfire appears, it’s best to diagnose and repair promptly.