Ignition Coil and Iridium Spark Plugs for Jaguar XJ8 (1999-2003) 4.0L

Direct-Fit Ignition Coil and Iridium Spark Plug Kit for 1999-2003 Jaguar XJ8

What it Does: Restores factory combustion efficiency and eliminates cylinder misfires by replacing degraded factory coil packs and worn plugs with high-dielectric coil-on-plug assemblies and fine-wire iridium spark plugs.

The Stock XJ8 Secondary Ignition Degradation

The Jaguar AJ-V8 engine positions ignition coils directly inside deep cylinder head wells sealed by engine beauty covers, subjecting the assemblies to extreme heat soak and thermal cycling. Over mileage, OEM coil insulation breaks down and rubber boots develop microscopic fissures, resulting in secondary voltage leakage to the head casting rather than the plug gap. This deterioration increases internal winding resistance, causing intermittent stumble, rough idle, and persistent P0300-P0308 diagnostic trouble codes under load.

The Engineering Solution

This 8-cylinder ignition overhaul kit features heavy-duty coil-on-plug units engineered with high-conductivity copper windings and heat-resistant silicone boots to isolate spark delivery and prevent arc-over. Paired with eight laser-welded iridium spark plugs, the package reduces ignition voltage requirements, broadens flame kernel development, and resists electrode erosion. Direct-fit blade terminals ensure plug-and-play factory connector engagement without harness modification.

Technical Specifications

Compatibility

• 1999 Jaguar XJ8 Base / L 4.0L V8
• 2000 Jaguar XJ8 Base / L 4.0L V8
• 2001 Jaguar XJ8 Base / L 4.0L V8
• 2002 Jaguar XJ8 Base / Sport 4.0L V8
• 2003 Jaguar XJ8 Base / Sport 4.0L V8

The Jaguar Precision Standard

Calibrated to match factory European OBD-II dwell and resistance parameters, ensuring consistent spark energy, balanced idle stability, and zero false check engine lights across all operating temperatures.