Mattsuzie,

Mine had the very same symtoms. It started out with slight shakes/vibrations at idle. As soon as I tapped on the gas, it's glass smooth again. For two years, I've tried (new OEM parts): engine mounts, transmission mount, plugs, cap & rotors, injectors (did try Redline, Chevron cleaners first); and the problem persisted, but worsening over the period. Took it to an independent shop a second time, found that it's indeed the fuel distributor (had previously thought it's the injectors - thus the replacements but they are originals (185K) anyway.)

Bought the re-man. distributor from germanstar.net (less than $500 bucks). Driving it home, all I could say is WOW...

You could check it by loosening each fuel line on the distributor (mine turned out to be no fuel output at all on cyl.#3 at idle - I learned it the hard way).

Hope this helps,
Frank.

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'86 560SEL | Silver Ext. / Blue Int. | 201K miles (Apr. 05) | 204K miles (Feb. 06)