Help 2000 E320 Running Awlful
 

Brought my 00 e320 in for a service(Brakes,rotors,air filter,feul filter,oil change
and run codes for check engine light.Shop called me and said all set.Got in the car and drove away.Car would not go over 20mpr and running awlful.
Seems it was running on 3 cylinders,with check engine light blinking.Brought
back to shop to re run codes,Cylinder mis-fire,.Tech feel its the 02 sensor now.Can this be?(should have gone to the dealer)Please advise!

I would advise finding a MB technician to deal with the problem. O2 sensor... give me a break.

More so than ever before, if you are paying for it, one should find a tech with at least the proper tools to work on the car. If a shop doesn't have a Star Tester then they aren't a Mercedes specialist. If they won't invest in the tool it also isn't likely they have invested in the training. O2 sensor... come on.

An o2 Sensor won't give you a misfire that quickly.
I'd very very worried about the people working on your vehicle.

Air mass meters have a tendency to fail and give very low power with delayed upshift. They don't leave fault codes relating to amm's, they do create codes relating to o2 sensors.

Disconnect your amm wiring and go for another drive. If it's better then it'll probably be your amm at fault