my experience resembles that described by Roger. my car is 99 E320 and it
has this convenience feature. some days, it just acts like it has a big luggee
in its throat. no pattern in ailment i.e. cold days, or rainy days etc.

what i havent done is to remove the cover and see if it might have anything
to do with clearance/obstruction issues.

about 5x a year, it'll exhibit this anomaly. but so far, it just recovers. absolutely
no pattern detected as to when/why it manifests in this manner.

__________________
-- raymond~
47º 34'N 122º 18'W