you can read the threads here and in other Jaguar forums to learn what models/years are the most troublesome, mine are old (and reliable) so I stay away from the modern models, but that's just me. I hear the 8 cylinder models have serious timing chain problems, imagine that, a car less than 5 years old, already needing a rebuild. Mine are 23 and 40 years old with the original engines still ticking fine... go figure! Just my opinion, but i am guessing all these problems have to do with Ford. But I don't know to what extent Jaguar is using Ford parts or engines, so take what I'm saying with some salt.

 

Well I have a 1993 xj6 that I have had for about 2 months, it has been very reliable so far.

What you should check is that the Air conditioner is working, that is a common problem, specifically the two inner vents.
make sure the engine runs good, check the brakes on ares they were old disks, so we had to pay over a grand to have the disks replaced.
Are car has ben fine tho, so check the xj40 or xj6 forum on this board and look thru it for more problems people have