1988 Buick Lesabre

Can you tell if it might be a tranny issue? Sometimes if the tranny is slipping, the engine might rev a little, without the vehicle increasing speed. Have you checked all the fluids? Does the engne feel like it is missing?

When was the last tune-up, you know, air filter, fuel filter, everything? If you change the fuel filter, make sure there is no pressure on the line, before you break anything loose. Can you check fuel pressure?

Since your obd 1, you should be able to check for codes, if there are any.