Join Date: Mar 2013
Location: West Wales, UK
Vehicle: Gone: 2013 SLK 55 AMG
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Exhaust problem and eco stop starts working
Just over a week ago I was out with my wife, giving the car a good run over some nice, fast, twisty welsh roads. I'd been behind a pretty obnoxious X5 driver who was coming to a virtual stop every time anything remotely resembling a bend presented itself, then pushing their foot through the floorpan as soon as they exited it. We'd just gone through a 30mph zone, at the end of which reverts back to 60mph on a straight. So I changed down to 2nd as we crossed the change and planted my right foot.
The noise was horrible: really metallic, raspy - just plain wrong.
The exhaust continued to sound very raspy all the way home. I'd liken it to the exhaust on an e46 m3 - like someone has filled the exhaust with ball bearings. The blip on downshift sounded like a buzz-saw.
Took it out the next day, the exhaust still sounded raspy, and the normal bass that kicks in over 2k rpm was obvious by its absence. Over 4k rpm it just didn't feel like it was picking up as it should and changing gear via the paddles in the higher rpm felt off.
My first though was it was a flaps issue, which would account for the change in noise and the loss of pull at higher rpms if the flow was restricted.
The car got trailered over to the dealer (I live 2 hours/100 miles away) - and then I had the dreaded phone call: they can't find any problem with it, it sounds fine to them. I kept explaining the problem, but they just couldn't see any issues. They even got someone else's 55 in to compare against and said they sounded the same.
Interestingly, one thing they did do was "enrich" the engine via STAR. They said they could do this and still be within MB tolerances.
They trailered it back to me and I took it out for a 12 mile drive - only to instantly know it still didn't sound right. I'd liken it to listening to the exhaust through a pair of cheap speakers - the bass was well down and the treble up on how it should sound. My wife was in the car and said it sounded "nice", but I could tell she wasn't convinced that I was right about the sound not being as it should.
Here's where it got weird though - on the return journey I fired the car up and it was instantly apparent the sound was back as it should be. My wife had an "oh yeah" moment as it was very obvious that there was a ton more bass again, the higher frequencies had lessened, and the 2k flap opening point was back to being obvious again. The car pulls as it should from 4k again too.
Been out in it again today and it's still sounding really nice - I think the enrichment has actually improved the bass slightly too. So all good there if it stays like this.
Weirdly today though, for the umpteenth time since having the car I drove it down our driveway and stopped at the gate. And the engine cut out. Given the car has stop/start, this shouldn't have come as a massive surprise - except I've driven 2,600 miles in the thing and not once has the stop/start ever shown as anything other than inactive when I've been in eco mode. Nothing unusual at all about today - lid was down as normal, car driven from cold - all of about 100 feet. start/stop was showing as "active" on the return journey too.
All very odd.
I really didn't like the feeling of not being able to prove that the car didn't sound right - so I've ordered a Zoom H1 sound recorder in the hope I can capture the sound when it is working as it should, so I can use that as a reference. None of the cameras I have around me capture the sound well enough for that purpose.
Gone: SLK 55 AMG (2013) Iridium Silver / Bengal Red / Black Ash