Hello. I have a 2007 Mercedes e350 4matic sport. It's making a knocking noise while trying to start it. It also have a burning smell coming from under it. I was told that the starter Is bad. I got the car in 2016 and I have never changed the starter. Some people told me that I threw a rod. I can turn the motor by hand and the oil doesn't smell burnt or nothing. Can get some of you guys opinion?