Hello family. I have a 97 xj6l approx 130,000 miles. The car will cut off while running after about 10-15 minutes. Sometimes it will restart almost right away..other times 15 -20 minutes later and sometimes not till hours later. Hennessy Jaguar had it for 2 months...said they replaced the ignition switch with a used one. Worked for a while ... now I'm back where I started. Please help if you can.....thanks.

Does your car cut out suddenly or does it stutter and stall somewhat first? If it stutters I would suggest that the problem is fuel. Possibly a suspect pump. Is your fuel filter clean? If it's clogged it won't help.

If on the other hand it just "dies", then I would lean towards an electrical fault. Ignition switch would have been a suspect, but failing that, a bad earth on the engine earth strap is worth looking at. Lots of posts on here recently regarding bad earths.

Start at the basics, fuel and spark/power are the two necessary requirements for your engine to run, and air of course.