Well, I have a 1985 380SE and even before my car developed the engine "miss at idle when in park and when first shifting into 3rd and 4th" problem I would notice an occasional side to side movement when I was setting at a stop light or something. Sometimes it does not do it at all. Heck, I may need some of that BG44k stuff.

I am still working on mine.... I have heard my problem could be a vacuum leak, fuel pump relay, spark plug wires, etc. So, my next purchase is a FPR, or at least try to test my car to see if that could be the problem. I also have an occasional stalling of the engine, but only when outside temperatures are above 70°, but spring and summer are coming, so I need to fix whatever this is.

John said, "assuming that the valve guides are not worn" - thats probably my luck and whats wrong with mine, as I have 269K and people wonder why I do not want to spend $$$ on this car.

I almost bought a 84' 300SD, with 335K. It had a horrible engine shake.... it would violently shake at idle, but with even the slightest acceleration, it would smooth out completely. I had no idea what what was wrong with it, as I came here and I was told it could be bad news (bad compression), vacuum leaks, bad injectors, or as simple as a bad motor mount..... more of that "wild goose chase" info.

SO- I bought a 1990 Lexus LS400, so I can relate to your statement about it being smooth as silk. My car had 245K when I sold it and the engine and transmission were still as smooth silk.... flawless. I would have to look at the tachometer to see if the engine was still running when I was at stop lamps. I sold it because my A/C evaporator went out, as was my radio (it would only work when outside temperatures were above 90° for some reason). I sold it to my grandfathers pharmacist, who crashed it a few weeks later.

I currently have a 2000 Toyota Tundra pickup, with the 4.7L V8, which is supposed to be based on the Lexus V8 design (which is actually the same engine used in the Lexus LX470 SUV). It too is as smooth as silk... you cannot even hear it run at idle and I have to again, look at the tach to see if its still running.