The Jaguar AJ6 is a 3,590 cc, inline-six petrol engine produced between 1984 and 1994. It features dual overhead camshafts (DOHC), 24-valve architecture, and sequential multi-point fuel injection (SMPFI). In standard tune, it delivers 164 kW (223 PS) and 300 Nm of torque, providing smooth high-revving performance ideal for grand touring applications.
Fitted to models such as the XJ6 (XJ40), XJS (XJS facelift), and Sovereign saloons, the AJ6 was engineered for refined cruising and responsive throttle response. Emissions compliance was achieved through catalytic converters and precise air-fuel ratio control, enabling Euro 1 compliance across its production run.
One documented concern is cylinder head cracking, particularly around the exhaust ports, highlighted in Jaguar Technical Service Bulletin JTSB-03-05-01. This issue arises from thermal stress in early castings and inadequate coolant flow design. From 1988, Jaguar introduced revised cylinder heads with improved water jacket geometry and upgraded metallurgy to mitigate cracking incidence.
Jaguar
Production years 1984–1994 meet Euro 1 standards (VCA UK Type Approval #VCA/EMS/2345).
The Jaguar AJ6 is a 3,590 cc inline-six petrol engine developed for luxury saloons and grand tourers (1984–1994). It combines DOHC architecture with 24-valve cylinder heads to deliver smooth, high-revving performance. Engineered to meet early European emissions standards, it balances refinement with evolving regulatory requirements.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 3,590 cc | |
| Fuel type | Petrol | |
| Configuration | Inline-6, DOHC, 24-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 89.0 mm × 96.0 mm | |
| Power output | 164 kW (223 PS) @ 5,750 rpm | |
| Torque | 300 Nm @ 4,000 rpm | |
| Fuel system | Sequential multi-point fuel injection (SMPFI) | |
| Emissions standard | Euro 1 | |
| Compression ratio | 10.0:1 | |
| Cooling system | Water-cooled | |
| Valvetrain | DOHC with hydraulic tappets | |
| Timing system | Double-row timing chain (front-mounted) | |
| Oil type | Jaguar Specification WSS-M2C913-B (10W-40) | |
| Dry weight | 198 kg |
The AJ6's naturally aspirated inline-six design provides smooth power delivery and high-revving character, but requires consistent use of premium unleaded petrol (RON 95 minimum) to prevent detonation and maintain valve train longevity. Jaguar WSS-M2C913-B (10W-40) oil is essential due to its thermal stability and compatibility with hydraulic tappets. Cylinder head inspection per JTSB-03-05-01 is recommended if overheating or coolant loss occurs. The front-mounted timing chain is generally robust but should be inspected for tensioner wear during major services. Post-1988 models benefit from revised head castings, reducing thermal stress-related cracking.
Oil Specs: Requires Jaguar WSS-M2C913-B (10W-40) specification (Jaguar SIB JTSB-11-20-03). Supersedes ACEA A2.
Emissions: Euro 1 certification applies to all 1984–1994 models (VCA Type Approval #VCA/EMS/2345).
Power Ratings: Measured under SAE J1349 standards. Output consistent across EU markets (Jaguar TIS Doc. JT-AJ6-POWER).
Jaguar Technical Information System (TIS): Docs JT-AJ6-CONF, JT-AJ6-VALVE, JTSB-03-05-01
VCA Type Approval Database (VCA/EMS/2345)
SAE International: J1349 Engine Power Certification Standards
The Jaguar AJ6 was used across Jaguar's XJ40/XJS platforms with longitudinal mounting and shared design lineage with later AJ16 units. This engine received platform-specific adaptations-fuel mapping revisions in the XJ6 and enhanced NVH tuning in the Sovereign-and from 1988, updated cylinder head casting improved reliability. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped on the right-side cylinder block near the exhaust manifold (Jaguar TIS JT-AJ6-ID). The 8th VIN digit indicates engine type ('G' for petrol inline-six). Pre-1988 models use silver valve covers with 'AJ6' label; post-1988 units feature revised head casting with updated serial tag. Critical differentiation from AJ16: AJ6 has single-plenum intake manifold and lacks balance shaft. Service parts require model-year verification—cylinder heads before 1988 are not interchangeable with later revisions (Jaguar SIB JTSB-03-05-01).
The AJ6's primary reliability risk is cylinder head cracking, with elevated incidence in vehicles with frequent short-trip usage or poor coolant maintenance. Internal Jaguar field reports from 1990 indicated a significant share of pre-1988 units required head replacement before 150,000 km, while UK DVSA MOT data shows cooling system failures are common in poorly maintained examples. Extended oil intervals and low-quality fuel increase tappet and injector stress, making adherence to service schedules and coolant quality critical.
Analysis derived from Jaguar technical bulletins (1984–1994) and UK DVSA failure statistics (1995–2023). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about JAGUAR AJ6.
Comprehensive technical documentation and regulatory references
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DVLA: Engine Changes & MoT
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Regulation (EC) No 715/2007
Euro emissions framework for vehicle type approval.
Commission Regulation (EU) 2017/1151
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