289cobra1

My 1998 r129 suddenly started running rough. Thought it might be the coils which I have replaced before. At first it was rough at idle but still had power, gradually it became worse. It appears the right passenger side middle two cylinders appear to be miss firing. I replaced the coils and it still run rough. Injectors? The car did sit over the winter, there is the possibility of faze separation of the fuel. Could the injectors be plugged. If so can they be cleaned or do they need to be replaced?