Mercedes Repair Questions? Ask a Mechanic for Answers ASAP
The P201C meaning is Misfire on cylinder 1. So please inspect the spark plugs, and replace the if necessary. Also switch the ignition coils around and check if the problem moves with the coil. If this does not help, i suggest to switch the injectors.
Found a new mechanic last night and he agreed with your diagnosis but aslo said it could be the fuel pump?
Usually in the case fuel pump failure, misfire is present at several if not all cylinders. If the idle is bad due to fuel pump, then there should be no power from the engine during acceleration. But the fuel pressure test with fuel filter replacement is definately a good idea.