loss of power in a 190E

just had a oil change in a 190E the car had been setting for awhile,and the car lost power while driving, black smoke was coming from the back,so i put two bottles of heat and some more gas because the car had been setting up, and had not been driven, it acts has if it can't burn all the gas that is being put out and it also idles up on it's own, please help in this matter.