Cruise control not working

The cruise control systems on the pre-1991/part facelift XJSs are somewhat unreliable, yet when in good order work very well. They can be identified by having a 5″ diameter rubber bellows device connected to the throttle pedestal via a rod, and sitting on the top of the engine on a bracket bolted to the back of the AC compressor.

This bellows usually leaks, and so the applied vacuum does not pull in the bellows. The fix is to remove the bellows and seal the lips to the steel plates with a flexible adhesive – or send it/the car to KWE! The second most common problem is drift of the set speed, where setting it at, say, 40 mph results in the car speeding by itself up to 50 mph or more, sometimes to illegal speeds which can be alarming! This is always due to the control module failing. While they can be adjusted with some difficulty, the root cause (failing tantalum capacitors) is not fixed, so it will fail again in due course. KWE has the knowledge and equipment to repair and calibrate these modules for £150 + carriage and vat. Please call us.