Hi All,
Recently my 1995 XJR6 (123,000 miles) has developed an issue with the auto box performance when I select sports mode. The auto box performs perfectly when in normal mode but when I select sports mode, the engine starts to cut in & out, does not rev correctly, gear changes are very erratic when trying to accelerate (and throttle does nothing to raise the revs, most times) and eventually the car slows and cuts out altogether. It's only when I switch back to Normal mode while it is still moving that driving reverts to perfect operation or if the car stops, it will start fine and drives perfectly in normal mode. Can someone please direct me as to what could be the problem now as the box behaved perfectly in both modes for years now. I'm quite capable of doing the diagnostic and repair work myself and have a spare XJR6 car for parts.
Regards
Martinxjr6 (Ireland)

 

If you have a spare one, I'd start by swapping the gearbox ECU and see if that makes any difference.

 

A thought: Could it be related to the transmission wiring harness that gets stressed if the transmission mount has deteriorated and allowed to stretch the wires? Is your transmission mount in good shape?

If so, there are several threads on that topic.

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Hi All.
Gearbox mounting renewed about 2 years ago and is in very good shape.
The symptoms seem to point to the TCM (Transmission Control Module) alright as it controls the ignition timing to some degree as well as the gearbox valves while in Sports mode.
In the meantime I'll attach my Jag diagnostics to the car (I suppose I should have done this at the outset) and see what that throws up. Not every fault is captured in these early X300's.
Then I'll try replacing the TCM with my other known good TCM from my spare XJR and if that works, great.

Thanks again.

 

I think there was a TSB EPROM update for the 1995 4L80E too. Not sure if that is applicable here, but FYI:

http://www.jagrepair.com/images/TSB/...lumination.pdf

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