[emiel01]

I had a really bad lurch in every gear.

The cause of it turned out to be a WRONG SPARK PLUG, believe it or not!

I bought the XJR with a misfire on cilinder 8. I replaced the coil and the spark plug with a Champion sparkplug which cured the misfire. After that the transmission started to act really bad with a lurch in every gear when giving it some throttle. After replacing the transmission fluid, filter and the seals of the mechatronic unit, and updating the TCM software and resetting the shift adaptations, the issue was still there, jut as bad.
A guy at a Jaguar garage told me he had someone in the shop with a bad coil and transmission problems, which were cured after replacing the coil. So that made me replace the spark plug which I replaced in the beginning. I replaced that Champion spark plug with a NGK plug and that fixed it. So it turned out to be that spark plug the entire time. My theory is that is was throwing some high voltage spike or something which threw off the TCM.
So never get a Champion plug for your Jaguar! That $4 plug cost me $570 on all the other things that turned out not to be the cause.

So bad coils or spark plugs might not be your issue, but I thought I post it here for other people who might have the issue I had. And spark plugs are cheap and easy to replace for $4 per plug... (Make sure you get NGK)