I haven't looked under our hood, and don't want to take off the air cleaner in case our 190E 2.3 might be similar, but note that the linkage you show is only the upper part. The throttle shaft is lower down, and I would expect that part of the linkage to also have a return spring. Look at the actual throttle body butterfly shaft, and see if the spring is missing from that.

Steve

__________________
'91 MB 190E 2.3
'08 RAV4 Ltd 3.5
'83 Lazy Daze m'home 5.7