This could be a few different things... I don't know about the 97, but it could be indicative of a vacuum leak. However, it could also be the "kick down" adjustment, which is that cable that runs from the throttle linkage, down to the transmission. However, while you're at it, replace the fuse on the TCU (Transmission control unit) which is located on the passenger side, under the dash (usually you will just see a random fuse sticking down for no reason, put a fresh one in).
On my old 89 I had the same problem, ended up being vacuum, but that was a very different animal, but I would guess the causes would be about the same.
