Ignition Coil and Iridium Spark Plugs for Jaguar XJR (1999-2003) 4.0L

Direct-Fit Ignition Coil and Iridium Spark Plug Kit for 1999-2003 Jaguar XJR

Primary Function: Restores factory spark energy, resolves high-load misfires, and stabilizes idle across all 8 cylinders on supercharged 4.0L AJ-V8 engines.

The Stock XJR Ignition Breakdown

The supercharged AJ26S/AJ27S generates substantial cylinder head heat soak within the cramped X308 engine bay. Over time, OEM coil boots degrade, causing dielectric breakdown, micro-arcing against the plug wells, and secondary winding insulation failure under forced-induction cylinder pressures. Worn factory plugs also develop excessive electrode gaps, driving up coil primary resistance and triggering P0300-P0308 DTC misfire codes, rough idle, and unburned fuel entering the catalytic converters.

The Engineering Solution

This matched ignition service kit provides eight heavy-duty coil-on-plug assemblies wound with high-conductivity copper wire and encapsulated in high-dielectric epoxy to resist thermal fatigue. Paired with fine-wire iridium spark plugs, this setup lowers required ignition voltage, improves flame kernel development under positive boost pressure, and resists electrode erosion. Factory-matched blade terminals and OEM plug geometry ensure exact plug-and-play installation without wiring modifications.

Technical Specifications

Compatibility

• 1999 Jaguar XJR 4.0L V8 Supercharged (X308)
• 2000 Jaguar XJR 4.0L V8 Supercharged (X308)
• 2001 Jaguar XJR 4.0L V8 Supercharged (X308)
• 2002 Jaguar XJR 4.0L V8 Supercharged (X308)
• 2003 Jaguar XJR 4.0L V8 Supercharged (X308)

The Jaguar Standard

Precision supercharged European powertrains require consistent secondary coil voltage to maintain tight closed-loop fuel trims. This complete refresh delivers factory-spec resistance values to prevent false misfire flags and maintain smooth power delivery without CEL complications.