The fuel guage goes to empty when tank is full. Seat belt clip busted, catalytic converter rattles. Rear wheel noise. Poor stereo sound, no room for rear speakers.
The engine idles rough on my 1.9 liter, but starts right up. The cataylitic converter was expensive to have replaced. The major problem with my Z3 is the gear ratio. Even in 5th gear the engine tachs over 3500 rpm at 65, too high for my standards. I tried to put taller tires on the car since they don't make any other gear ratio for the rearend, but the taller tires makes the wheels bow out like the car was lowered.
I had a '96 Z3 a few years ago... while the car was underpowered and it suffered some quality control problems, I still found it fairly entertaining. Long trips were out of the question, however, due to its limited cargo space.
Wouldn't mind owning a later model year (with the 2.3L or 2.5L V6) as a second car.