1993 nissan altima cuts off at stop sign not sure how or what to fix?
Is the engine running poorly, or does it just cut off when you're coming to a stop with your foot off the gas? When it stalls, does it start back up again? When it starts, does it stay running in or out of gear? Has the check engine light come on at all? These answers can help narrow it down.
If the check engine light has come on with the engine running you need to scan the system, get the trouble code (s), and repair that problem first.
If it runs fine but stalls when coming to a stop, and starts right back up again, there can be several causes like a bad IAC valve, EGR valve hanging up, etc. But a very common problem is excessive carbon deposits built up on the back of the throttle plate, which requires a simple service (cleaning).