Buy Subaru Forester Spark Plug Wire Sets

• Sends 20,000-40,000 volts from the coil pack to each spark plug at the exact millisecond needed for combustion.
• Insulates that voltage with thick silicone or EPDM rubber so it does not arc to engine metal spark-plug wires basics .
• Acts as a resistor to tame radio-frequency noise that would otherwise scramble your ECU or radio signal design details .

The Forester's flat-four (boxer) puts two cylinders on each side of the bay. Subaru numbers them 1-3 on the passenger side and 2-4 on the driver side cylinder map .

• Early Foresters (1998-2013 EJ-series engines) use a four-wire set that clips to a top-center coil pack.
• 2014-up FB engines move the coils onto each plug, so they have only short jumper boots, not full wires.

• Subaru tune-up charts put spark plug wires in the 30,000-60,000 mile check column Car Care Council guide .
• Many owners see trouble around 70 k miles in hot climates, sooner if oil leaks soak the boots Forester forum report .
• Subaru bulletin 11-104-17 warns that worn wires can trigger random-misfire codes P0301-P0304 service PDF .

• Hard starts, stumble, or flashing CEL under load Kelley Blue Book symptoms .
• Visible cracks, swollen boots, or white arcing tracks.
• Measured resistance above 20 kΩ per wire NGK tech note .
• Snap, pop, or blue sparks dancing in the dark when you mist the wires with water DIY test video .

← scroll table horizontally →

Core styles: carbon-impregnated string (OEM suppression), spiral-wound alloy (low resistance), or classic solid-copper (vintage racing). Copper has near-zero resistance but no EMI control core comparison .

Factory EJ25 wires typically measure 7-12 kΩ end-to-end; readings above 15 kΩ mean the carbon core is breaking down Outback forum data . One owner posted 10-15 kΩ per foot as normal Forester thread . Always check each wire with a digital multimeter from terminal to terminal.

1. Label old wires 1-4 before removal to avoid cross-firing wire-routing note .
2. Twist the boot, then pull straight-never yank the cable.
3. Match new wire length to old; too long encourages arcing, too short strains the boots.
4. Press boots onto coil and plug until you feel or hear a click.
5. Route wires in factory looms and keep them off hot exhausts.

• Misfire after a wire swap? Double-check firing order 1-3-2-4 cylinder order video .
• Engine still shakes? Inspect coil pack cracks or corroded grounds.
• In wet climates, smear a pea-size dab of dielectric grease inside each boot to seal moisture Wikipedia design note .

Swapping a tired set can restore lost mpg, smooth idle, and cut tail-pipe emissions. Owners report easier cold starts and snappier throttle response once resistance drops back into spec community feedback .

• Detailed EJ25 engine wiring diagrams (service manual PDF).
• NGK's online catalog for wire-set construction specs.
• Subaru's misfire troubleshooting bulletin for code P030x NHTSA link .

With the right spark plug wire set and a bit of DIY care, your Subaru Forester can keep its famous boxer rumble strong for years to come.