My own car gives me nothing but trouble so it's not just you
Only just sorted a gearbox cable that slipped of a little bush that hold it to gear selector and it felt like the whole diff at back only holding up on a single loose bolt, gears were all over the place!
Then x300 has this plastic intake breather/resonator, can't remember whether xj40 has it, it basically split right in the middle in a little hole it has and created a 3mm hole each side and an air leak. Took me 2 or 3 weeks to locate it! I knew it has an air leak, just couldn't locate it as it was in a such an awkward place. Of course the car misfired on petrol and stalled often when getting to a stop, I was ready to pull the fuel pump out of the tank...
Luckily I have lpg on which it ran ok so wasn't stuck completely.
Still love that damned car
1997, 4.0 LWB X300 - Unlucky car but still a daily driver.
1988, 3.6S XJS - Never ending restoration project.
1994, 3.2S X300 - Accident damaged, October 2015. Gone!
1994, 3.2S XJ40 - Long gone.