The cause is probably very simple, but it's the dramatic consequences that make it seem that much worse. Don't sell it b/c you're frustrated. More often than not, once you get rid of it, the new owner might get lucky, find the simple cause of the problem, and fix it and have your car how it was before the problem started (which was in great shape I assume). Take it to the dealer if you have to. btw it sounds like a simple fuel delivery problem. Something must be stuck open, like an injector or something. Could even be a vacuum line. From my experience, however, it sounds like a simple but hidden problem or failing component. Good luck!
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'94 854 N/A.