Originally Posted by LandYaghtLover

I had a simliar, if not same issue, with my 560SEL. In my case it was the fuel tank purge system. When I was doing engine lambda adjusting I had to remove the purge line. The car would idle great. But once I hooked the line up my reading were all over.

Basically it was a vacuum leak that was "controlled" by one of those temp sensors things that the vac lines go through. When cold, that line was closed off. But when warm, it would usually be open and I would have the issue.

Anyway, once I plugged the black line with white stripe (larger tube by the way) my issue was gone. And my milage is way up. And I feel warm and fuzzy inside. But now my charcoal can might bite the dust.