In a small bowl, combine 2 tablespoons flour, salt, and pepper. Coat the short ribs with the flour mixture.

In a large skillet, heat the olive oil over medium-high heat. Brown short ribs in olive oil.

In a slow cooker, combine onions, wine, chili sauce, brown sugar, vinegar, Worcestershire sauce, mustard, and chili powder. Mix thoroughly. Transfer the short ribs from the skillet to the slow cooker.

Cover, and cook on Low for 6 to 8 hours.

Remove ribs, and turn the slow cooker control to High. Mix the remaining 2 tablespoons of flour with 1/4 cup water, and stir into the sauce. Cook for 10 minutes, or until slightly thickened.