The sensor from the benz bin is as follows:
AT Protection Switch
From what you stated, do you mean that cylinder #4 is mis-firing, instead of position #4? I think thats what you meant. This could be cause by a number of this. It is most likely a bad wire. If thats the case, you just replace it. Not a hard job. It also could be a bad wiring harness. How is your wiring harness? Im sure your aware of that issue with these cars. Mine isnt in the best condition, but it works for now.
The crankshaft position sensor I dont believe to be bad. If it didnt work, the engine would not run. So I would rule that out, unless anyone has experienced intermittent issues with one??
How many miles are on your car? If I were you, what I would do is start from scratch. Clear out all the codes. Start it up, drive around the block, then recheck them. Chances are, something will tripped and it will spit out a code. These computers are very precise in narrowing down things. Once you get the codes we can go from there.
In the meantime, you might want to framiliarize yourself with the computer interface and the various computers. Here is a web page that I learned how to do it from. Its a great resource and a convenience and hats off to the maker of it. Its is...
Those are for a 95 S500 but the majority is the same for our car. Your going to want to scroll through sections 2, 5, 6, 7,8. Print out the X11/4 Pin Map (round) in section 2. You will need that for reference when you pull the codes. We will only be using pin #'s 4, 6, 7, 8, and 17. Does your car have ASR? When you buy an analog volt meter...pick up a few short wires with alligator clips on them. They will make things alot easier in the future. And get something that will fit into those metal pinouts on the round connecter, like a metal pick or something small. I dont know if the volt meters ones will fit, they are usually too thick. Pull the cap off the computer box and check it out for yourself and you will see what im saying. They are quite small. In case you dont know where this port is, its where the battery is supposed to be, on the passenger side firewall. Its a big black box with a round plug on top that you can unsrew, kinda like a radiator cap.
Let me know when your ready and I can help ya. Good luck.