Hi all, first time posting here and I hope someone can help me sort through a C300 I inherited with a CEL/Code P0496.

Brief history before I inherited the car:
car was at MB dealership for "rough running engine"
MB says shutoff valve of charcoal canister stick in the closed position during guide test/vacuum test
MB says replace charcoal canister but the original owner declined

Owner brought it to an indy shop that replaced canister shut off valve, mass air flow sensor and purge solenoid.

I inherited the car, filled the gas tank (pump stopped normally with a click). Engine started super rough, choked and died. I had to hold down the gas pedal to get it to move out of the way.

I cleared the engine codes but I'm left with permanent codes P0496 (evap high purge flow), P0171 and P0174 (system too lean) that keep coming back. Engine starts a little rough but otherwise idles/drives OK. Everything I read leads me to either think the purge valve or the vapor canister needs to be replaced (even though the indy shop says it was replaced before I got the car).

I hope someone can point me in the right direction! Thanks!

 

The P0171 and P0174 typically are engine vacuum leaks, probably unrelated to the EVAP issue. Try tracking those down.