Misfiring Cylinders?
 

As I was reversing out of the drive today, my C63 14 plate started feeling very juddery and making odd clunking sounds. I could feel jolts coming through the accelerator as I went forward (in C mode) through to 4th gear, but the acceleration was like it was on half power i.e. normal revs but what felt like half the power. It felt like the engine was seizing up or about to. The engine management light flickered then came fully on.

I turned the car round and back on to the drive. Popped the hood and you could see the engine block juddering in idle. When I gave it some gas the same thing, really weird noises, a bit of spluttering and it felt like only half the engine was working. Exhaust fumes were coming out of all pipes.

Turned off the engine and got on the phone to Merc roadside. I started the engine so the operator could hear how deeply troubled the engine was and...it was completely fine!!

I'm no engineer, but I wondered if it was a software **** up that made only one bank of cylinders fire? Or something else? Anyone else had any experience like this or thoughts on what it might be?

Cheers.

Will

The same thing happened to me recently and lasted about ten days before it suddenly stopped. The puzzling thing was no codes were thrown. Mine was at cold startup though (60º ambient) and I drove through it, meaning once I got up to 2k RPM in second gear I just held it there as best as possible. The motor would return to normal operation after water temps reached about 120º each time but the shaking and lack of power with nothing to go on (codes) was disconcerting to say the least.

Mine did exactly that a few months ago. The universal first step of tech support (turn it off and then turn it on again) fixed it for me too. It hasn't happened since. I wonder what causes it....

Thanks guys, seems like this mystery is going to go unsolved for now.

If you search the site there are several threads on this. About 6 months ago mine started occasionally and got progressively worse until it was almost daily. Culprits have been O2 sensors, fuel injectors, plugs and I changed them all and it didn't fix my problem. I would also try removing the air boxes and spray cleaner on the MAP sensors and removing all the fuses and relays in the engine compartment box and also the wires from the 4 ground points in the engine compartment and clean them and apply a thin layer of dielectric grease. That is what cured my problem.

Did you scan it? If the cel came on it probably stored a code(s). Misfire will be a p030x (generic scanner), x being the cylinder it's misfiring on.