what could make my car shutt off when slowing down or stopping
May help to clean throttle body.
where would it be located
^^TB and any of your sensors before or near your TB that read air flow or temp or other parameters to input to the computer how much fuel is needed. If it runs good otherwise then it shouldn't be idle air control valve related (IAC) but do your research on how to clean your specific one before attempting.
I have a 1992 ninety eight and had same problem. I changed the mass air flow sensor and now runs fine.
Looking for a Used Ninety-Eight in your area?
CarGurus has 27 nationwide Ninety-Eight listings and the tools to find you a great deal.
Search Oldsmobile Ninety-Eight Questions
Oldsmobile Ninety-Eight Experts
Related Models For Sale