4.6 Dinan Idle issues
 

Did a search, couldn't find a thread that describes the same issue. Comes and goes, but sometimes, the car either doesn't WANT to idle (Starts, cranks over, and then dies) or idles very irregularly (surges, falls, sometimes dies at a red light).

More usually, it happens when there is no load, in P or Neutral. It will happen as you coast to a stop at a light. If it just sits and idles, it will surge, and fall, and sometimes die. Mechanics have searched for a vacuum leak (which was my first theory) and found nothing. Wondering if there's an idle sensor of some sort? This is the ONLY issue with an otherwise awesome car. Any suggestions much appreciated.

Any codes?
I don't mean just CEL. BMW advanced tool should be able to get some codes stored in DME.

my car did the same thing, and no check engine light, Replaced the MAF and all was good

I'd still advise trying to read stored codes if any. There could be numerous reasons for symptoms like that and he might resolved it by replacing MAF but it could easily be something else.

UPDATE: problem solved (I think)

Codes pointed to lean mix errors- Have always suspected vacuum leak, and finally found it- pipe under supercharger had come loose from the clamp, but only in the bottom (where it was virtually impossible to see).

Re-fit everything with a new clamp, runs like a champ.