One problem related to rear suspension shock absorber has been reported for the 1998 Mercury Grand Marquis. The most recently reported issues are listed below.
Vehicle became undriveable due to the fact that the air suspension completely gave out and the shock absorbers were no longer working. The approximate starting time to this problem, when the compressor was acting up, was back in September of 2010. The car sits so low to the ground now that I will have to get rid of it altogether (either have a junk yard buy it or get rid of it as a parts car), as it's unsafe for me to drive, let alone have my daughter in. Also, I'm a poor mother, unemployed, who definitely can't afford to pay the large costs of getting this fixed. In talking to people about the problem, it's either the compressor has gone bad, a wiring problem, or a problem with the on/off switch in the trunk.