W203 rumbling

[nAN3992]

Hi again

I have an update on the subject.
I lifted my car at the local shop, and it's missing a catalysator and front muffler, there is nothing there, only a straight pipe that someone (I suppose the previous owner) welded instead (see pic). So, I think that's what causing the rumbling sound.
As for why it got worse after rear muffler replacement, the new muffler is not original part but some cheap replacement part that hasn't got the same muffling capability.
You also mentioned that your problems began after exhaust repair, so check the front muffler.
Please excuse my English.

Hey,

I checked the underside of my car. There is only one muffler at the end. In the middle, near the transmission there is a flex pipe. Above that, in the engine cabin ( under the air filter ) there is one more box. I believe thats the dpf filter? Yes the sound began after they took the exhaust off. First at it was hardly noticable, but with time passing by its getting louder. Only on cold weather, at certain rpm. ( when i try to accelerate at lower rpm ) once above 1500 rpm the sound is gone.