I don't have an 88-89 but there must be a constant supply of power in order to maintain the memory when the battery is disconnected. Is it possible that there is a small internal battery some where just for this purpose? After all these years it may have finally quit. Just a thought.
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steve,
91 coup (white with white trim, medium beachwood interior)
91 convertible (white with white trim, saddle cloth top and medium beachwood interior)
91 coup (white with black trim, medium beachwood interior)
90 coup (driftwood)
Anybody looking for a southern California car, feel free to contact me. Lots of rust free cars here.