,any recourse? have been unable to contact previous owner

sry u got ripped

You spent 800 dollars on a 1997 BMW? Not a bad deal, spend a little more to get it fixed.
If the repairs cost 800 dollars, then just add that into the cost of the vehicle.
Any person to person car sale has a Red light warranty...
...When the red lights go over the hill, warranty is over.

You still have a good car, so don't disparage your momentary bad luck.