I searched threads with idle problems trying to identify my idle problem, which was different than yours.
What I found over and over again is that the throttle actuator is a common failure part. When the throttle actuator goes out, the cruise control goes with it. The fact that your cruise control is not working along with a bad idle is not a good sign.
Hopefully it's something else.
This would not be good news as the throttle actuator is about $1,000.
2001 E430, Bourdeaux Red, Oyster interior.
1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".