Ignition Coil and Iridium Spark Plugs for Jaguar XJ8 (2004-2009) 4.2L

Direct-Fit Ignition Coil and Iridium Spark Plug Kit for 2004-2009 Jaguar XJ8

What it Does: Restores factory ignition timing, eliminates high-load misfires, and stabilizes idle by replacing worn primary ignition components on the 4.2L V8 platform.

The Stock XJ8 Thermal Breakdown and Voltage Leakage

Due to severe underhood thermal cycling in the enclosed AJ-V8 engine bay, factory ignition coils suffer from insulation fatigue, dielectric breakdown, and micro-cracking across the epoxy potting. This thermal stress causes internal winding resistance to drift out of specification, producing intermittent spark loss, rough idle, and unburned fuel entering the exhaust stream, while standard plugs experience rapid electrode gap widening.

The Engineering Solution

This 8-cylinder refresh kit pairs heavy-duty coil-on-plug assemblies with high-efficiency fine-wire iridium spark plugs. The replacement coils utilize dense internal copper windings, heat-resistant thermoplastic housings, and corrosion-resistant blade terminals for maximum conductivity and thermal stability. The included iridium spark plugs resist high-temperature erosion, reducing required firing voltage and delivering a focused, consistent flame kernel under all load conditions.

Technical Specifications

Compatibility

• 2004-2009 Jaguar XJ8 Base Sedan 4.2L V8
• 2004-2009 Jaguar XJ8 L Sedan 4.2L V8
• 2005-2009 Jaguar Super V8 4.2L V8 (Naturally Aspirated/Supercharged Coil Cross-Reference)
• 2004-2009 Jaguar Vanden Plas 4.2L V8

The Jaguar Precision Standard

Engineered to meet stringent European engine management tolerances, this ignition service kit prevents check engine lights (CEL), restores factory fuel trim maps, and provides seamless cold starts with zero modifications required.