My E320 developed a noticable vibration at idle (500 rpm). It is not as though the engine developed a miss, it's more like an out of balance vibration. It goes away at higher rpms.

It smooths out a little when I shift into neutral (700 rpm), but it also smooths out in Drive at 700 rpm.

I opened the hood and watched the engine as I shift from Drive to Reverse. There is no big jump of the engine.

Could it be worn engine mounts?

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95 E320 Cabriolet, 159K

If it feels like a miss, it probably is. Motor mounts will transmit all engine vibration to the chassis, not just the "out of balance" sensations. Does this car still have a distributor or does it have the coil packs? When's the last time it got an ignition tuneup?

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Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

The car has coil packs. I had one go bad some time ago, so I know what that feels like. This is more subtle and only at idle. Otherwise, it runs smooth as silk. Like I said, it is not a miss. Ignition tune up is current, but due soon in 4000 miles.

Fixed! I installed new Lemfoerder motor mounts and now the engine idles smooth as silk.

The job took me 1.5 hours. The car sees no salt so I didn't have to fight the fasteners.

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95 E320 Cabriolet, 159K