That happened to my sister's G20. It was the bearings in the alternator. We took it to an alternator shop to get them replaced. Since it's a PITA to get the alternator out, we put in new brushes too. The whole job was cheap and it now runs (and sounds) like new. Neall. '93 G20 - 1/2 turbo install, 5th gear pop-out, blown trunk struts