What caused rough idle and sometime engine of Fun?

Question

Rough idle, engine may die during low rpm.  STFT -15%.  But, driving is fine.

Answer 1

STFT at a negative 15 % you have a running rich condition. The first approach is to check for any fault codes that may be set. BMW has had problem with the DME for a loss of power during idle or when slowing to a stop, with no fault code stored in the DME. The fix in these case is to reprogram the DME. TSB # SI B 12 15 07 titled N52 Loss of Power