Finally found where shutter is coming from
 

The vibration or shuttering is coming from the plastic engine cover when idleing in gear.
The minor engine miss, as I call it, causes the plastic cover to rattle or shutter. When in neutral the engine purrs. When put in gear, the engine cover shutters from side to side.


New spark plugs installed but still shutters.

Motor mounts or damper.

What are you working on?

Sorry, It's a 2003 E320.


It's been shuttering for several months but only when you stop in traffic. After the engine runs for about 20 minutes it usually clears up and idles smooth,


I was thinking about a bottle of fuel injector cleaner. It started when my wife started putting 87 octane to save money. We only use 93 octane now but it didn't clear up.

As I stated in another post quoted below, 87 octane did not cause the car to have a run problem nor will it have caused any damage. Modern cars will reduce ignition timing to compensate for the lower octane.

The short story is take it to a competent shop and let them fix it, you will just be guessing and randomly changing parts.

https://www.peachparts.com/shopforum/tech-help/396561-2003-c320-running-rough.html

Old 12-19-2018, 07:34 PM
97 SL320
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Join Date: Jan 2012
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97 SL320 is online now

Better buy her something good for Christmas, regular fuel won't cause a rough idle. About all that will happen is a slight reduction of max power due to ignition timing reduction. At part throttle you won't likely notice a difference.