Two problems related to catalytic convertor have been reported for the 1998 Mercury Mystique. The most recently reported issues are listed below.
Horn does not work. Vehicle has been checked by dealer several times. Horn would work intermittently, but currently it has failed completely. The rear seat belts are inoperative. The power steering, alternator, and front brakes failed. The catalytic converter caught on fire.
Problem with unpleasant fumes entering vehicle. Vehicle has been in shop on four occasions, and problem still reoccurring. Feel free to provide any further details.