2014 C250 turbo. Finally got an CEL code P0030 number 3 misfire but it only occurs when you are accelerating and slowly press the accelerator more than half way without pushing into high RPMs. The car starts to buck and feel as if it’s a manual stuttering in first gear when you don’t give it enough gas starting off. It’s intermittent and then sometimes it’s steady. If you let it go ling enough it kicks the engine code and goes into a safe mode until you turn off and crank the car again. If you drive it like a granny, it runs like a top. Really need a good diagnosis.

 

Have you pulled the plugs and checked cylinder 3. If it's on that cylinder and you have the code you know where to start at least. It's rare, don't get me wrong here, but I had that once and I finally pulled the plug to find out the ground electrode had broken off inside the cylinder. Check the basics first, fuel, air and spark.

 

Bad plugs or bad coil maybe (on these cars one per cylinder) When combustion pressure rises on power on the spark is "blown out" ---- but works ok when slowly power on or revving in neutral because the combustion pressure are lower without the resistance by trying to showe the car.
Same symtom can often be seen both when coils or spark plugs are bad.
But start with the most likely and the cheapest culprit first, namely spark plugs. Especially if they have done tens of thousands of miles already...
I have expirienced this a number of times through the years - latest before i pulled the plugs on my E280T - the were worn but otherwise looked okay, with no deposits and a nice colour. The plug gap were over 2 mm so no wonder the "gave up the ghost - or spark ;-) .. when accelerating hard. 6 new ones mounted and all is fine --

 

There was a defect regarding this, I think it had to do with fuel pump or fuel pressure regulator or fuel filter...can't remember but it was about fuel delivery. Make sure yours has the work already performed. Most people experienced it accelerating to either get on a freeway or pass someone on a freeway.

 

OP did you ever get this issue resolved? I’m having the exact problem.

 

No. Just keep driving it. It'll reset out of 'limp mode' after a day or two. Or, there's a reset procedure with key/ignition position, lights on/off, wiggle your ears, and it resets the ecu...but I've given up on that. i've even disconnected the battery...worked first time, not the second.

 

well for what it’s worth I had the exact same problem and replacing all the coil packs did the trick. Runs like a peach again!