cenzo86

I'm only 131 hard miles so far. No babying beside a 5 mile drive on eco mode.

DapperStyle

I say schedule a dealer visit. Maybe it is indeed best to follow the break in procedure from the manual, it'll be interesting to see what the dealership says though.

inhartwetrust

It would also contradict MB's own touting of the "signature AMG soundtrack" from the exhaust.

cenzo86

Appointment is on Monday. I also want them to fix the wind noise from the drivers side door.

Sma2c

I hope one of the other dealerships will be able to figure this out. I have little hope that the dealer here will.

Albanmtexas

https://m.youtube.com/watch?v=wvJS0lm3nlc

Mike5215

It's telling that the car is losing the crackle on its own irrespective of any mechanical intervention. While I don't believe the ECU has any adaptive capacity to learn how you drive and adjust itself, the tranny does. Since the over-run is triggered in part by a hard downshift, it's possible the TCU is inadvertently changing its shifting behavior in a way that prevents the over run from having any effect.

Might be worth doing a TCU reset to see if it helps:

Procedure Reset Transmission Adaptive Learning DIY

Turn the key to position 2. You should see all the dash lights come on. ...

Press the gas pedal all the way. ...
Wait. ...

Turn key to OFF, position 0. ...

Release the gas pedal.

Wait 2 minutes. ...

Start the car and drive.

cenzo86

I tried that twice yesterday. No change. The first time I held the pedal down for 5 seconds before switching off and recessing. The second time I held down for 10 seconds. No difference in sound or feel.

z28lt1

Anyone try just disconnecting the battery for a while and see if anything resets? Have no idea if it will actually work, but this seems to be something that is changing over time...

DapperStyle

Just a tip and likely won't fix your issue but it's still good to know. After resetting your TCU you need to drive like a bat out of hell for a while and then turn the car off, next time you start it up it will be much more responsive.

With my W204 I take it out on the backroads or to the hawk's nest and I'll reset my TCU before I do a few runs and by the time I'm through and turn the car off and back on you can feel a massive difference.

katlis

Just wanted to mention I've been having the same problem recently too. It's intermittent, but in Sport+ while driving down my parking garage it shifts at way too low of an rpm. So as I'm driving slowly it feels like its in some sort of limp mode if I try to accelerate, until I get out on the street and force it to downshift. Then the crackle comes back randomly after several minutes of driving. Wasn't like this when I first got the car.

cenzo86

Just a follow up here.
I took my car to the dealer on Monday and drove with their tech foreman. My service advisor just reached out with the following: The bad news is it will not be ready today, the better news is, it will be ready tomorrow with all the correct noises from the exhaust. We were advised to reprogram the engine computer with new coding values. Something in the computer that was not seeing the higher rpm to allow the valves in the exhaust to open and close.*
Now I know based on reading every post on this site, that the c450 has a traditional exhaust without any valves. I don't see any reason to call bull**** yet because up through now, they have agreed that the vehicle is not operating within spec. Maybe they messed up and are currently installing the controllable system from the c63. In which case I will be entirely satisfied!

Mike5215

Hmm. Maybe he's referring to the timing to open the exhaust valve early in the cylinder head itself, to allow the unburned fuel to enter the exhaust manifold.

cenzo86

Problem solved. Below is the dealer service record for anyone who's dealer needs help diagnosing the issue.

Sma2c

Good to hear they were able to correct the issue for you quickly. The dealer that worked on my car remains clueless and has been "working with Germany" for about a month... I sent them the detail you provided (thank you) though they will not have an opportunity to work on my car again.

cenzo86

Best of luck to you. There are a couple of codes on that sheet that may mean something to your tech. It might even be helpful to have them contact my service center directly: Rallye Motors of Roslyn.

Zed512

Well old thread I know, but my car has just stopped making the crackling noise in Sport +. Very odd.
tried the reset procedure and will see if it comes back in the next fews days of driving. Otherwise, another trip to the dealer.

Sma2c

Good luck Zed, please let us know how it goes. It came back for me after 2-3 months just out of the blue. It then stopped again and I have not heard it in several months.

Zed512

Crack is back... just time and diving in Sport plus seemed to bring it back.