1992 Buick Century 1992 Buick stalls when slowing down and

The car stalls out after it runs awhile(Warmed up). It will start up in park or neutral, but it will stall again as soon as you put it in gear (Like you turned off the car). It seems to be that when I'm slowing down the car starts shaking and it stalls. I've been able to prevent this by down shifting when slowing down, but eventually it will stall. I've been told that it could be a automatic transmission solenoid, but I would like a second opinion.