For several months our 2003 E320 has been running rough as I called it.

Over the last few months, I changed the 12 plugs, put in fuel injector system cleaner and changed where I by fuel, but the missing as I called it, slowly got worse.

My wife finally watched an online video of a MB shaking while in gear. It was motor mounts failure.

Yesterday, I changed out the E320's engine mounts here at home and found the problem.

The drivers side mount was bad and had been leaking slightly.

What seemed like an engine miss to me turned out to be a bad motor mount.
Just to help someone else out I posted this.

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1998 Land Rover Range Rover 66K Miles
1988 300SE Totaled in 1998, hit by drunk driver, but we walked away OK
1989 420SEL 140,000, just warming up. Total by 18 wheel gas truck rear ended, but refused to lose another MB. Had it repaired cost $10,000+ Great Car again SOLD it for a 2003 C320 to save on gas
1991 2500 Suburban 454, 130,000, Best truck in the world. SOLD it out right.
1952 8N Tractor 1,000,000-/+

I forgot to say..

The engine runs so smooth now when we stop at a light, it sounds like the engine stops. We got so used to a rough idle and it was the engine mounts all along.

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1998 Land Rover Range Rover 66K Miles
1988 300SE Totaled in 1998, hit by drunk driver, but we walked away OK
1989 420SEL 140,000, just warming up. Total by 18 wheel gas truck rear ended, but refused to lose another MB. Had it repaired cost $10,000+ Great Car again SOLD it for a 2003 C320 to save on gas
1991 2500 Suburban 454, 130,000, Best truck in the world. SOLD it out right.
1952 8N Tractor 1,000,000-/+

I had the same thing happening on my 560SEL, replaced the motor mounts, and it smoothed out for a couple of years. Now it was running rough again, this time a vacuum leak on the plenum seals. I am replacing them right now (a massive job), and one of the seals separated in my hand, with the inner ring detaching from the outer ring. What a mess!

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Henry Bofinger
1989 560 SEL (black/black)
2001 Audi TT Roadster (silver/grey)