M104 engines do not have an idle speed control module.

It is part of the throttle actuator, which is also called the ISC / EA / CC module:

Idle speed control
Electronic accelerator
Cruise Control

If your throttle linkage is not screwed up, and if your idle isn't hunting around, then I'd have to assume something is wrong with your actuator.

__________________
Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".