I have a 1998 XJR with only 60,000 miles on it, however, a couple time after I picked someone up at the airport or filled up at the gas station, I can't seem to start the car (it starts, but takes a long time while it struggles to start), as you can imagine, it is embarrassing to not start in such a beautiful and luxurious car. I have been told this might be a nikasil liner problem, or a throttle body problem (but this was cleaned at 45,000miles), or spark plugs, I would like to know what would probably be my best bet before plunging more money into this thing.
It is possible that the nikasil is the problem but not likly. It was a issue but I diid not see to many super charged motors with nikasil go bad. It is possible and I think this is the problem that the secondary timing chain or chains let loose. Causing the timing on the camshafts to be off. This is a very common problem with the older cars. I work for a jaguar dealer and this is what I have seen by your description. Any other questions feel free to email me at thedeerhunter30