Oxygen Sensor failure.
Various Bulbs blow out every couple of weeks.
Fore/aft power adjuster for passenger seat is faulty.
Some dash lights out, and it looks like it will be a lot of trouble to replace them.
Edge of passenger seat has wrinkled due to heat exposure, a common issue with these cars.
This has been a very worthy car for our family. It has been very reliable so far and we have had complete confidence in it on many long trips. This is my dad's car and I recently took it on a 600 mile trip where it performed flawlessly.
We were lucky enough to purchase this car from a certified Jaguar mechanic who replaced many important components prior to sale that are known to fail. These parts include: the rear differential (about $1200), head gasket, brake components, and all-new updated relays. He also had the remote entry/alarm system recoded which is a feature that often fails on Jaguars of this vintage.
If buying an XJ40 Jag, do avoid the '88-'91 years unless you find one that is just fantastic and treat yourself to a '93-'97 XJ6. '94 was the last and best year of the XJ40 body style and by the time ours was made, the electrical system had been converted to Bosch from Lucas and the engine increased in size and durability. One nice touch was that ours was recalled before we bought it and it now has the 2002 engine control module that allows fuel economy upward of 24-26 MPG. It still uses premium however.
Update: It is gone now! We sold the beautiful old girl. I miss it, but oddly enough, not that much. It was starting to need some things. These cars get quirky as they get older and we decided that we had had our fun and it was time to quit while we were still ahead. It will make a fine car for the new owner and I can now say that I have owned a Jaguar, and what an experience! I will own another someday.
We're about to sell our 1994 XJ6 and I can now say good riddance. It was an awesome car to drive, and I have never had such a smooth, quiet ride. However, the repair bills start adding up, and it isn't worth it. Driving a Jaguar certainly is a great experience. OWNING a Jaguar is not nearly so fun.
Yes, unfortunately these cars still had some frighteningly expensive parts. Ours was very reliable for the year that we had it, however the previous owner had put a lot of money into preventive maintenance. Ours was starting to need some things with the rear suspension, and other things were creeping up, so we decided to sell it while we were ahead. We sold it for about half of what we paid, which was not much, and came out happy that we had a year of trouble-free Jag ownership. Also, we probably put about 30,000 miles on the car in that year because we loved it SO much and drove it EVERYWHERE!!!