I met another mercedes owner tonight at a local restaurant, the car he owns is a 1983 240D 4 speed. He said he is having acceleration problems so I just told him the 240's are slugs anyway. Well I took it for a test drive and there is a horrible vibration at idle, makes my 300D seem smooth as butter. Once you take off and gain some rpm, the vibration goes away but once you idle it's back. What should I look for that can be causing this? I have never felt a car vibrate this bad in my life.