Idling issues
Sounds like a vacuum hose for me. I've got the same problem moths ago but with the newer engine M271 (c200). I'm with manual transmission but I don't think is different with the automatic. I had the same idling issue when my car is on neutral going up and down but if I go with gears was totally fine. Changed MAF,Sparks,Coils,Acc Pedal and some other things with no luck xD. And one morning | decided to take a better look on the engine hoses, for my surprise I found one broken hose " CRANKCASE GAS HOSE", I translated it from my language so probably this is not the real name of it. And man after I fix it the problems with idling stoped immediately so I think is the same with you but who knows. I added you some photos but remember its not the M111 Engine it is M271.
Last edited by AlexGeorgiev; Jan 10, 2020 at 10:31 AM. Reason: adding photos
Georgiev above has posted excellent advice to ensure that all engine vacuum hoses are in good condition. They frequently deteriorate at their ends where they are connected to something, then develop a crack which defeats the purpose of the device connected to.
I don't think from the sparse information provided, that it is a bent valve.






