Jaguar XK Catalytic Converter

The catalytic converter in Jaguar XK models (XK8/XKR) is a crucial component of the exhaust system designed to reduce harmful emissions. The V8 engine has two cylinder banks, each with its own primary catalytic converter, mounted vertically just after the exhaust manifolds on each bank. Exhaust gases flow from the engine through the manifolds, then pass through the catalytic converters before continuing to the central and rear silencers. The catalytic converter transforms carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOx) into less harmful gases like CO₂, H₂O, and N₂ using a ceramic or metallic honeycomb substrate coated with precious metals such as platinum, palladium, and rhodium.

Jaguar XK catalytic converters are equipped with oxygen sensors positioned to manage engine mixture and monitor catalytic efficiency. Typically, there is an upstream heated oxygen sensor (Position 2) before the catalytic converter that controls fuel mixture. A downstream oxygen sensor (Position 3) is present mainly in North American markets to verify catalytic converter effectiveness. Some Japanese market models also use a temperature sensor as a downstream sensor in Position 4. When replacing or modifying catalytic converters, it is important to consider the exact placement of these sensors and the length of their wiring harnesses for compatibility and to avoid fault codes.

Removing the catalytic converter from Jaguar XK8 models involves careful steps due to limited space and corrosion risks:

• Locate and identify the catalytic converter mounting points, including a slide-fit connection to the exhaust line, a motor/gearbox support bracket secured by two M10 bolts, a collector flange with three fixing points, and O2 sensors screwed into the converter body.
• Left side access is generally easier, using long extensions and special sockets to reach bolts and connectors.
• Right side access is restricted by the steering rack and may require removal of the air duct and use of specialized tools.
• Carefully disconnect O2 sensors with a 22 mm wrench; unplug connectors located underneath the dashboard behind the throttle body.
• Prepare in advance with penetrating oil to loosen seized nuts and studs, and be prepared to loosen or partially remove heat shields for better access.

Note that sometimes partial removal of the exhaust system may be necessary to free the catalytic converter due to deep slip joint connections.

For Jaguar XK owners seeking improved engine performance and sound, sport catalytic converters with reduced cell density are available:

• 200 Cell Sport Catalytic Converters: These have larger cells (honeycombs) than OEM units (which usually have 400+ cells). They reduce exhaust backpressure, improving flow and adding measurable performance gains, along with a more aggressive V8 sound and reduced weight.
• 300 Cell Sports Catalytic Converters: Offer a balance between flow and emission control, delivering significant power and torque gains while maintaining effective emissions compliance. These are designed to fit original mounting points and sensor locations.

Such sport catalytic converters typically bolt on to existing exhaust systems without modification and are popular for combined road and track use, often paired with ECU tuning.

Some Jaguar XK owners consider universal catalytic converters for cost savings. However, several factors require attention:

• Tube diameter and flange dimensions must match the vehicle's exhaust system.
• Oxygen sensor positions and thread locations must be adapted precisely to prevent diagnostic trouble codes (e.g., P0420) and check engine lights.
• Welding and installation angles must replicate the original layout to avoid exhaust stresses.
• Legal compliance depends on certification standards (e.g., ECE/R103, EPA/Carb) and local regulations.

For these reasons, universal catalytic converters require professional installation and validation for compatibility and legal use.

Removing the catalytic converter on a Jaguar XK for use on public roads is generally illegal across Europe and many other countries:

• Emissions control laws require functioning catalytic converters for passing technical inspections and pollution standards.
• Removing the converter triggers fault codes due to downstream oxygen sensor readings, illuminating warning lights and possibly restricting engine performance.
• Noise and exhaust odor increase significantly without the catalytic converter.
• For track or competition use only, some owners remove the converters but usually install sport catalytic converters instead of complete removal to balance performance and emission regulations.

Always check local laws and vehicle regulations before considering decat modifications.

The original Jaguar catalytic converters are expensive and can be prone to issues due to corrosion and age. Signs of a failing catalytic converter include:

• Loss of engine power or a feeling of choking.
• Unusual noises such as rattling or scraping indicating broken internal substrate.
• Diagnostic trouble codes related to catalytic efficiency from the OBD system.
• Significant increase in exhaust temperature and fuel consumption.

Replacement options include genuine OEM converters, certified aftermarket units, sport catalytic converters, or professionally adapted universal catalytic converters. Prices vary widely depending on quality and supplier.

Several high-quality resources provide detailed technical information and step-by-step tutorials for Jaguar XK catalytic converters:

• Specialized Jaguar XK8/XKR catalytic converter removal videos showing different model years and sensor locations.
• Illustrated manuals providing standard exhaust system disassembly and reassembly procedures with torque specifications.
• Technical sheets explaining oxygen sensor placement and catalytic converter designs.
• Forums and owner clubs offering real-world advice, troubleshooting, and shared experiences on replacements and upgrades.

It is recommended to consult professional technical support or authorized service manuals when working on your Jaguar XK exhaust system for precise information and warranty compliance.