One problem related to o2 sensor has been reported for the 1997 Hyundai Elantra. The most recently reported issues are listed below.
02 sensor replaced on 8-6-01, b/u light switch replaced on 8-6-01,ignition coils repl. On 9-21-99, engine check light been reset 10 times,#1 & #4 not firing 10 times or more, car looses power, chugs then dies 2 times.