Jaguar AJ126 (3.0 supercharged V6)

Jaguar Land Rover's supercharged 3.0 V6 — the AJ133 V8 with two cylinders removed — in the F-Type, XE, XF, Discovery and Range Rover Sport. It shares the V8's block architecture, its Roots supercharger sitting in the vee, and most of its service character.

AJ is Jaguar's prefix for every engine it has ever built and carries no family information at all. The AJ-V8, the AJ16 straight-six and the Ingenium four and six all share it and share nothing else. The straight-six that replaced this engine is an Ingenium, a completely different design, and a reader looking for "the Jaguar 3.0 six" may want either.

The supercharger has its own cooling circuit with its own electric pump, and that pump is the fault worth knowing: when it fails or its coolant is neglected, charge temperature climbs, the engine pulls timing, and the car simply feels slow with no code and no noise. A supercharged JLR V6 that has lost its edge is the intercooler circuit before it is anything expensive.

The timing chains and their tensioners are the other recurring item on earlier engines, presenting as a rattle at start-up. And the crankshaft damper can work loose — a vibration that is easy to attribute to mounts and is not.