Miss-firing losing power

1984 chev citation 2.5 auto coming home on the intersate the other night my car started losing power and miss-firing and engine light came on, pulled off the highway and did a quick check found nothing a miss started back up car ran fine until about 2 miles from home and it did it again. The car runs fine in town but at times on the interstate I have this problem more and more can you help. Ive changed the air filter to no avail