Hello, when I started my Smart Forfour 1.3 today, the whole car was very busy. The speedometer varied greatly between 400-800 revolutions. The engine wobbled very strongly and had hardly any gas consumption. I then started it again and it ran again as usual. However, the engine control lamp was shining and I drove to the workshop where a fault diagnosis was made. Mistake: engine control unit! The mechanic has made the car several times on and off. Sometimes the engine had this unround run, sometimes it ran normal. So, according to the workshop, the engine control unit CAN be over, which is not exactly cheap What should I do now? Can you buy the part used as well?