Ignition Coil and Iridium Spark Plugs for Subaru Forester (2004-2009) 2.5L

Direct-Fit Ignition Coil and Iridium Spark Plug Kit for 2004-2009 Subaru Forester

What it Does: The Ignition Coil and Iridium Spark Plug Kit replaces degraded factory secondary ignition components on the 2004-2009 Subaru Forester to restore combustion efficiency, eliminate cylinder misfires, and stabilize idle quality.

The Stock Subaru Forester Thermal Breakdown Vulnerability

The horizontally opposed layout of the EJ25 places the coil-on-plug modules and spark plugs in extreme proximity to the cylinder heads and exhaust manifold heat shields. Over operational cycles, severe engine bay heat soak degrades the internal copper windings and dielectric epoxy of the factory coil packs. This thermal stress causes micro-fissuring in the silicone insulation boots, resulting in secondary voltage leakage to the cylinder head wall, elevated resistance, and erratic spark delivery under heavy engine load. Concurrently, standard electrode erosion on aging plugs widens the gap, placing excessive electrical strain on the coils and triggering P0300 through P0304 diagnostic trouble codes.

The Engineering Solution

This comprehensive tune-up kit features heavy-duty coil packs wound with high-conductivity copper magnetic wire encased in thermal-resistant dielectric resin to withstand sustained head temperatures. The paired fine-wire Iridium spark plugs utilize a high-melting-point laser-welded electrode tip, requiring lower firing voltage while projecting a stable, concentrated plasma kernel into the combustion chamber. Engineered as a direct drop-in solution matching OEM resistance specifications, this kit restores rapid flame-front propagation, sharpens throttle response, and shields against high-temperature voltage tracking across the entire SG and SH generation engine cycles.

Technical Specifications

Compatibility

• 2004-2008 Subaru Forester 2.5L H4 (SG Chassis, EJ25)
• 2009 Subaru Forester 2.5L H4 (SH Chassis, EJ25)

Frequently Asked Questions

Does this fit the SG and SH Forester?
Yes, this is a direct fit for the 2004-2009 Subaru Forester equipped with the EJ25 2.5L engine.

Do the iridium spark plugs come pre-gapped for the EJ25?
Yes, the plugs are factory-gapped to OEM clearance specifications, though verifying gap with a non-contact gauge prior to install is recommended.

The Subaru Boxer Reliability Standard

Boxer-engine powertrains demand exact ignition timing and uncompromised secondary voltage to maintain balance and eliminate low-RPM hesitation. Built for rigorous all-weather driving and prolonged thermal resistance, this ignition package delivers the uncompromised combustion consistency required by Subaru AWD platforms.