Way too many things; more than any other car I've known:
Crankshaft balancer dented; replaced it with new, $200.
Crankshaft sensor must have had recurring problems, which caused the car to stop suddenly at any time on the middle of the road, without any reason. It was removed by the previous owner.
Air conditioning never worked; would have cost at least $250 to repair.
Fan (passenger area ventilation) was unstoppable; the climate control unit must have failed.
Power steering kept on losing oil all the time.
Various oil leaks around the engine and the transaxle.
Automatic transmission died -- typical FWD Chrysler problem. Cost me over $1500 to have it replaced. I should have sold the car to the very first junkyard at this moment, instead of repairing it!
Cruise control - vacuum pipes got loose, fixed quickly.
Fuses, relays, various electronic parts failing all the time.
Crankshaft bearings died -- typical 3.5L engine problem. At that point, I just had enough and traded the car straight away.
I bought my LHS because I had been dreaming about an American cruiser for years. However, this dream then turned into a NIGHTMARE. Here's the lesson I've learnt...
Soon after I bought it, it started to produce serious signs of problems. And as soon as I had one thing repaired, another part failed. No matter how carefully I drove, something always happened. And repairs on this car can get expensive very easily, simply because it's complicated.
Mechanically, this car WAS a pain. Almost every important part is undersized, or prone to errors / failures. The 3.5L engine is known to have constructional problems, even the later models, and parts are not cheap. Crankshaft, bearings, sealings, connecting rods, and of course the army of sensors -- just a few common and recurring problems.
The automatic transaxle is perhaps the WORST part. When it works, it works real fine, shifts smoothly. However it can cause a headache any time, being way too weak to move such a large car with such an engine. And of course it's front-wheel drive, so it's costly and time-consuming to remove the transaxle in case of repairs. Also it can have sudden electronic problems, which will prevent it from upshifting from 2nd gear ("limp-home mode"). No matter how carefully I test-drove the car (twice) before purchasing, the transmission broke into pieces when I tried to back up to a parking place, and had to be completely replaced. And even the replaced transmission switched into "limp-home mode" once or twice.
On the bright side: when the car worked, it was "cool". Traveling - and also driving - was a pleasure, it had enormous space for five adults. The leather seats were very comfortable, and surprisingly, didn't wear out even after 15 years. From the inside, the car was almost flawless. The trunk was also large and had a flat floor, which was very practical. Acceleration was decent with the V6, and it was reasonably quiet inside. It was also a safe car to be in: traction control and ABS were standard, just like the two airbags.
Bottom line: I was lucky to be able to trade this car, for about third the money I've put into it! I really wanted it to be a dream car, so drove and maintained it the best I could... And still, I was literally afraid of using the car lately, since I never knew what would go wrong after the next mile.
Beware of front-wheel drive Chryslers of the '90s. I think will never buy a Chrysler again.