Hello!

I purchased my first MB about two weeks ago, a 2005 C55 AMG with 83,000 miles.

Last Wednesday night, I noticed the acceleration and shifting to be a bit sporadic and unpredictable. It felt a little slow in places, a little jumpy in places, and not as smooth as the first week of ownership.

The next day, on two separate occasions, the car would lag in acceleration from a stop, not moving at all, and then surge forward all at once. Then, at a stop, the engine cut off completely. Not violently, I just looked down and the lights were on and the engine was not. I cranked it, it sounded rough, I turned it back and cranked it again and it fired up. I immediately went to a German shop about a mile down the road and explained the issue.

Friday morning, I receive a call that he was unable to replicate the issue I had described and that the car seemed to be performing as expected. He did, however, smoke test the car and find a vent hose to be split near the intake. He seemed unsure if this was the cause of the issue I had described, but we agreed to replace it.

Today, I spoke to him on the phone again and he mentioned that the hose was on the car and he was, again, unable to replicate an issue. He did mention however that the exhaust seemed a bit loud to him and that he could smell the catalytic converter. He asked if I wanted to put it on a lift and test the system. I told him to standby; I have had the car inspected pre-purchase twice and neither inspection showed any issues beyond a leaking rear main seal, trans pan, worn control arm bushings, and lipped rotors. The car is not throwing any codes for cat or a CEL.

If anyone has any insight into whether the issue I experienced is related to the vacuum leak he found, or if it is worth checking out the cat, please let me know.

Thanks!

 

Nice to see that temporary ban I asked for you to receive changed your attitude.

Oh well, we got about 3 good months without this crap.

 

I’m obviously new here—is this the level of helpfulness and productivity I can expect?

 

Only from him. We're a tiny subset of a much bigger model, so be patient and someone with real knowledge of your issue will pop in.

Have you had codes pulled because they can pop up and disappear? Obviously, you usually see them before they disappear, but still.

 

I don't have any real solid answers, but first of all I wouldn't suspect cats at all. I can't envision any scenario where bad cats would cause such a severe symptom that is also intermittent. Plus, I think you'd have the CEL on with a "catalyst efficiency" fault code.

Could have been the vacuum leak for sure, particularly with a split hose. The splits can sometimes open and close as the engine mounts let things move around a bit.

If the problem continues after having the vacuum leak corrected, pay attention to whether the issue is related at all to ambient temperature, and whether the engine is stone cold, at full operating temperature, or somewhere in between.

Also, just in the interest of eliminating the most obvious and basic things first... make sure that this "when you step on it, it almost nothing happens then it suddenly takes off" issue isn't just the traction and stability control interfering. Because that's exactly what my C32 feels like with ESP enabled, particularly pulling out onto a busy road - while the wheel is cut, there is almost no power and the ESP warning triangle flashes like crazy, then once things are straightened up and it gets traction it surges forward with everything it's got. It was alarming the first couple of times it happened, until I realized it was just the ESP. Trying the same with ESP "off" lets you get up and go a lot quicker but you better be paying attention and be ready to countersteer. And your passenger better have a change of underwear handy, lol.

 

Thanks a ton for the reply -- I was similarly really skeptical of the cat diagnosis. It seemed like conjecture with no basis, which surprised me coming from an extremely reputable German specialist. I talked to him this morning and he is convinced that the cat is an issue, if not the issue causing the surging and cutoff. I agreed to have him lift it and diagnose -- at this point I'll pay $120 to prove him wrong.

The power lag then surge was not a traction issue. Foot on the pedal caused no rise in RPM whatsoever, until it did, if that makes sense. It felt like the engine was off, even thought it wasn't. Tech said he was unable to replicate the issue I described after installing the intake hose, but he also said that before installing it.

I'll update this soon. Thanks again!

 

If you're going to keep replying like a petulant child, I'm going to keep tattle-telling like one too. Reported yet again.

You don't own any of the vehicles for the subforums you continuously jump around to, leaving the meanest, most unhelpful posts possible just this side of an outright ban. Why? What is missing from your real life where that is remotely necessary?

 

The vacuum leak could have easily caused the stalling issue. I would also suggest checking all your plug wires on the coil side. On my C55 @ 75k miles I had to replace a few wires and a coil because of corrosion, water got in and the connector between plug wire and coil became rusted and disintegrated.