The Jaguar AJ20 is a 2,967 cc, inline-six, naturally aspirated petrol engine produced between 1996 and 2003. It features dual overhead camshafts (DOHC), 24-valve configuration, and sequential multi-point fuel injection, delivering 177 kW (240 PS) in its standard tune. This engine was part of Jaguar's modular AJ-V6/AJ-V8 family, designed for smooth power delivery and refinement in executive and grand touring applications.
Fitted to the XJ (X308) and XK (X100) models, including the XJ8 and XK8 variants, the AJ20 was engineered for a balance of effortless cruising and responsive performance. Emissions compliance was achieved through sequential fuel injection, three-way catalytic converters, and integrated engine management, allowing it to meet Euro 3 standards across its production run.
One documented technical concern is degradation of the camshaft sprocket locating dowels, highlighted in Jaguar Technical Service Bulletin JAG-TS-2418. This issue, primarily affecting high-mileage engines, can lead to cam timing misalignment and subsequent engine misfires. From 1999, Jaguar introduced a revised sprocket design with improved material hardness and retention, reducing field failure rates.
Jaguar
Production years 1996–2003 meet Euro 3 emissions standards (EU Directive 98/69/EC, VCA UK Type Approval #VCA/JAG/AJ20/1996).
The Jaguar AJ20 is a 2,967 cc inline-six naturally aspirated petrol engine engineered for luxury saloon and grand tourer applications (1996–2003). It combines DOHC architecture with sequential fuel injection to deliver smooth, linear power and quiet operation. Designed to meet Euro 3 standards, it balances refinement with mechanical reliability.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 2,967 cc | |
| Fuel type | Petrol | |
| Configuration | Inline-6, DOHC, 24-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 89.0 mm × 80.0 mm | |
| Power output | 177 kW (240 PS) @ 6,100 rpm | |
| Torque | 285 Nm @ 4,100 rpm | |
| Fuel system | Sequential multi-point fuel injection (Siemens MS 4.2) | |
| Emissions standard | Euro 3 | |
| Compression ratio | 10.0:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | Not applicable | |
| Timing system | Double roller chain, duplex primary with simplex secondary | |
| Oil type | SAE 10W-40 mineral or semi-synthetic (Jaguar Specification WSS-M2C159-B) | |
| Dry weight | 192 kg |
The naturally aspirated design provides linear throttle response ideal for relaxed driving but requires regular high-RPM operation to maintain combustion chamber cleanliness. SAE 10W-40 oil meeting Jaguar WSS-M2C159-B is critical for chain and bearing lubrication. Extended oil change intervals increase risk of cam sprocket wear due to degraded oil film strength. The Siemens MS 4.2 engine management system demands stable battery voltage; low voltage can disrupt fuel injection timing. Post-1999 models feature improved cam sprocket retention, reducing timing-related faults. Catalytic converters are sensitive to leaded fuel and misfire events, necessitating prompt diagnosis of ignition faults.
Oil Specs: Requires SAE 10W-40 meeting Jaguar WSS-M2C159-B (Jaguar SIB JAG-OIL-1996). Supersedes ACEA A2/A3 standards.
Emissions: Euro 3 certification applies to all 1996–2003 models (VCA Type Approval #VCA/JAG/AJ20/1996). Three-way catalyst required for compliance.
Power Ratings: Measured under ECER 85 standards. Output reflects engine-only test with full exhaust system and emissions controls.
Jaguar Technical Information System (TIS): Docs AJ-ENG-20-001, AJ-ENG-20-003, JAG-TS-2418
VCA Type Approval Database (VCA/JAG/AJ20/1996)
European Directive 98/69/EC
The Jaguar AJ20 was used across Jaguar's XJ/XK platforms with longitudinal mounting and no licensed external applications. This engine received model-specific tuning adjustments-sequential intake manifold on the XJ and revised exhaust manifolds on the XK-and from 1999 the facelifted X308 models adopted updated cam sprocket hardware, creating interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine serial number stamped on the machined pad at the front of the right-hand cylinder block (Jaguar TIS AJ-ID-001). The "AJ20" designation is cast into the cylinder head near the cam cover. XJ8 models feature a transverse-mounted configuration with compact ancillary layout; XK8 units have revised exhaust routing. Critical differentiation from AJ-V8: The AJ20 has a 30° cylinder bank angle and absence of secondary air injection. Service parts require model-year verification—cam sprockets for pre-1999 models are incompatible with post-1999 revisions due to updated retention design (Jaguar SIB JAG-CAM-1999).
The AJ20's primary reliability risk is camshaft sprocket dowel degradation in high-mileage vehicles, with elevated incidence in poorly maintained examples. Jaguar internal field reports from 1998–2004 noted a significant number of XJ8 models requiring cam timing repair before 140,000 km, while UK DVSA MOT records show misfire and emissions faults as frequent causes of advisory notices. Extended oil intervals and thermal cycling accelerate wear, making correct oil selection and service adherence critical.
Analysis derived from Jaguar technical bulletins (1996-2003) and UK DVSA failure statistics (2000-2023). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about JAGUAR AJ20.
Comprehensive technical documentation and regulatory references
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DVLA: Engine Changes & MoT
Official guidance on engine swaps and inspection implications.
Vehicle Certification Agency (VCA)
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Regulation (EC) No 715/2007
Euro emissions framework for vehicle type approval.
Commission Regulation (EU) 2017/1151
WLTP and RDE testing procedures for emissions certification.
GOV.UK: Vehicle Approval
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