Can anyone tell me what might be causing this problem? I have a 1992 300D with just over 78000 miles on the clock. The engine has been
running smoothly, and I've got good oil pressure. I change the oil religiously (synthetic), and servicing has been strictly by the book.

When coming back from lunch today, driving at about 30 miles per hour, a knock started (almost like the normal clatter when the engine's cold but more pronounced), and the engine started running rough. I was a block from my office, so I crept a block and a half further and parked the car, which is now being towed to my mercedes shop.

Aside from something major, like a rod going, could this be symptomatic of something as simple as a fuel injector going bad, or getting clogged? I try to put regular highway miles on the car, but it does see a lot of local driving.

I hate to think of the cost of a replacement motor for this car which could run to $8000.

TIA for any and all suggestions/info,

--Duncan