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Discussion Starter #1
http://www.billsden.org/fileadmin/media/mercedes/slk/docs/dtb_p_b_07_61_48.pdf

If you receive customer reports in the above model vehicle of rough idle (engine vibration through vehicle body) with shift lever in position “P”, it may be caused by the idle speed being too low and/or engine mounts
being too hard.
To correct proceed as follows:
1.Increase idle speed to 720RPM (engine at operating temperature).
and / or
2. Replace engine mounts with part number listed below.
2 Engine mounts A211 240 27


I'm not sure if this is my particular problem but I am experiencing a rough idle after starting the car, with the shift lever in position "P." The idle speed in "P" appears to be at around 750 or so and then it drops to 500RPM with the shift lever in position "D." Sometimes when starting the car in the morning, some white smoke shoots out of the exhaust for just a few seconds.

Video:


Techron has already been used, spark plugs (and valve cover gaskets) changed, and engine mounts checked out OK according to PPI performed. Is STAR Diagnosis my next step? Do indie MB shops have access to STAR and what if no software updates are found?
 

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Sorry that I can't help here James other than to say:

"Ahhhh, the beauty of a new "used" car. It's kinda like starting all over again......." I know you well enough to know that even the slightest shake is going to drive you nuts. Maybe just take it to a dealer to get these little "quirks" all worked out until she's just the way you want her, then back to the indies?
 

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I was about to ask whether you are completely sure that it is not the ordinary slight vibration from the engine. But as this question is stupid in your case, I would suggest to check the exhaust system or the fans.
 

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Discussion Starter #5
Having never owned a SLK55 AMG before, I'm not sure if this is normal for the 'beast' under the hood. The 350 definitely has a smoother idle if that's the case. I'm not even sure if the previous owner(s) have added any aftermarket engine software. My service advisor says I'm welcome to leave the car with them overnight so they can do a cold start the next day. I'm getting the Eurocharged ECU tune soon. Not sure if I should bother with any software updates before then.
 

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When I start the 55 in the morning (cold engine), the initial rpm goes to 1250 rpm and stays there for may 30-45 seconds, then gradually goes to 750 rpm. I cannot characterize it as rough idle. The shift lever in on P.
 

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Hi James. My son had a Mach 1 Mustang that burned oil over time. This was normal. White smoke came out of the exhaust at initial start up. I believe higher idle is just warming the engine.
 

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Discussion Starter #9
Do you feel the rough idle, or just hear it?
I feel it. Maybe the car does not like to idle-lol. Usually I put it in "D" after the initial RPMs have dropped to 750-ish. I thought I'd idle for 2 minutes to let the car warm up when it's been really cold outside.
 

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James did you get it sorted as I am having a similar issue?
 

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Hi James.

In addition to your PM, I can make the following comments.

The whine I hear at start-up, definitely sounds like a worn alternator (but it can't be because I had it replaced and it still sounds exactly the same), but trying to be a bit more objective is difficult, as the sound sound disappears after a few minutes when the engine is warm.

At initial cold start, I experience very little vibration, certainly not enough to feel and within a couple of minutes, it's so smooth as to require me to check the tacho that the thing is still running - it's that quiet and smooth. Not the merest tremble, almost to the point that I wish it was a little more 'lively'. It's the smoothest V8 I've ever owned and idles as silkily as the I6 in my 300SE. You could rest a brim-full glass of wine on the hood and it wouldn't spill.

Frankly, I think as others have suggested, if you're not happy, spend $100 for 30 mins diagnostic at MBUSA and see what they find. It's only the cost of a tank of gas...
 

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.....
The whine I hear at start-up, definitely sounds like a worn alternator (but it can't be because I had it replaced and it still sounds exactly the same), but trying to be a bit more objective is difficult, as the sound sound disappears after a few minutes when the engine is warm.
...
This is usually the high speed air pump that sends air to the catalytic converters to start the process and heats them up for their intended work.
 
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