I had the same symptoms on mine - at idle/low rpms, it shook. Smooth while driving. Turned out to be the engine mounts. For an '88, if you haven't had the mounts replaced, they're due.

If you have the common front timing chain cover oil leak, oil can get into the distributor cap and cause a rough idle as well, from fouling the contacts.

__________________
Chris
2007 E550 4Matic - 61,000 Km - Iridium Silver, black leather, Sport package, Premium 2 package
2007 GL450 4Matic - 62,000 Km - Obsidian Black Metallic, black leather, all options
1998 E430 - sold
1989 300E - 333,000 Km - sold
1977 280E - sold
1971 250 - retired

"And a frign hat. They gave me a hat at the annual benefits meeting. I said. how does this benefit me. I dont have anything from the company.. So they gave me a hat." - TheDon