About 1 month and a half ago i had a problem with my 155 2.0 16V to start. My mechanic said that the problem was the fuel pump which was supposed to be changed and worked well until 4 days ago. When the car did not start 4 days ago i realised there was no current going to the fuel pump. After i changed the fuel pump relay with a new one, the car started perfectly but it was revving too low (below 600 RPM) and finally switching off. I went for a drive and i noticed that the car worked perfectly over 1000 RPM. But when the car was left idling, it was knocking and finally switching off. Can anyone help ?