Agreed-- they are flummoxed by that as well.

Not something I'd know enough to rule out, but, yeah-- hopefully not!

Zero-- car ran beautifully, during normal driving and under all kinds of acceleration, I picked up zero symptoms other than the knocking sound in the video above that drove me to bring it in, engine never sounded at all strange to me, except after cold-start idle and even at that was somewhat intermittent and engine had to be cold.

​​​​​​​Thanks for the continuing support
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repair detail:

What ever happened to Cyl #8 issue. LOL. How is she sounding now?

Probably fair to assume it's *exactly* as you surmised upthread (confusion.)

Utterly delicious!
I bought and had them put in new engine air-filters (no real reason,) and they changed oil and I was driving a GLC300 for the last week, SO, we all know how that goes-- felt so damn good to be back in there that I can't distinguish what's what other than "oh my god, I missed this thing!"

Will have to wait for a cold-start to know if the noise is gone, they said there was no trace of it this am. Regardless, whatever it was/is, it led to the discovery of this problem, which I'm pretty glad about.

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Good to hear brother. These beasts were meant to be enjoyed. Drive it like you stole it. LOL

Thanks and willdo!

And, my bad, one clarification; there was a separate line-item on another page for repairs to cylinder 8, w/ injector replaced etc due to "cold start misfires"-- sorry about the bad info.

GREAT NEWS, and kudos to your MB dealer for sticking with it and getting it resolved..

Hey, as long as its fixed thats all that matters.

Got a slightly different version of the sound and car has a bit of a shake to it when parked and running. Doesn’t need to be cold anymore to manifest itself.

Well that just sucks bull nipples. It might show "random cylinder misfire". Or they might of not reinstalled something correctly but that would of or should of shown up right away, but not always.
Something as simple as a loose clamp on intercooler tube will make the car run like crap. Man i feel for you, wish you were in my area as I would love to look at this thing and see what its doing.

current mood:

Hey Jon, any progress with the misfire noise gremlin?

I can't say I have an actual strategy here, but, for now, driving it around, ignoring it when it's present, and then will take it in to dealer after about a month to check and see if there are misfires again and/or maybe inspect the spark-plugs, etc. Feels like maybe the noise is a belt as suggested, at this point-- very unclear to me how that plays in with the misfires that were discovered (complete coincidence vs some other theory.) But, in any case, will be checking it frequently while not wanted to just have it spend whole week(s) at a time in the dealership vs. me sorta putting my head in the sand for now and driving (and enjoying the crap out of) it as I normally would.

Whatever it is it will rear its ugly head soon enough. Until it does, do what you are doing in enjoying it.

Didn't you mention that in the beginning the car preformed well but you would hear the noises that bothered you? Its under warranty for awhile so drive it hard (NOT abuse) , if it is something major it will, as mentioned show itself. Have you talked to your MB dealer and told them the latest?

Took the car back in as I basically planned, plus the other day cold idle was a bit ugly and uneven.

They noted same and have replaced all the remaining injectors and all the plugs, will report back. Thanks as always!

Ask them to keep car overnite so they can verify true cold idle after sitting overnite.
Good luck.

Yes, absolutely, they did a cold start yesterday morning, that led them to put in the parts today, now keeping overnight for a cold start tomorrow morning , definitely not trusting anything shy of 12++ hours of sitting.

So I left the dealership on Friday without taking a copy of the paperwork, when I have a PDF of it, will post the actual work performed.

Mean time, I was told (again to be verified once I have the actual paperwork) that: all (remaining? (not sure)) plugs, coils and injectors were replaced.

I haven't driven it much since I picked it up, but, from the drive home and a few short drives since, I'd tentatively say the idle is -much- better at cold start and I think I'd say much better overall. There's a smoothness there that I guess I just didn't even realize had gone missing, I guess it degraded over time, then the knocking sound showed up, then the first repair didn't do all that much, and, now, it feels beautiful to me all of a sudden. Will continue to report back.

Speaking of smoothness and not realizing how "off" something was; the rear wing mechanism was replaced and is MUCH quieter, smoother and less obtrusive than it was/had become. I feel on that one, it was either a) never right from the day I received the car, or, b) degraded over time. It was quite chattery and kinda squeaky (or a "howl" almost) and it also was *constantly* re-latching itself (that's what it sounded like anyway,) when doing driving that didn't even remotely require the wing to deploy.

Jon, is she running as she should be now I hope.

At present, absolutely-- never better!

i'm glad that this was all under warranty, as it would have been expensive!