Update:
Despite what I posted previously the 'reset' didn't quite sort it, it was a bit better but still had a tendancy to stumble if the throttle was tickled at idle which in turn could make it stall or bog down when pulling away.
Whilst in for warantee work I had the dealer look into it (Chelmsford, essex). On a short test drive their mechanic agreed something was not right but computer diagnostics did not show any sensor or fault codes to indicate a problem. BMW HQ gurus were consulted and suggested a update of the DME software/code would be the best course of action as thats simple to do. For those who don't speak BMW, the DME is the engine control computer. After flashing the DME they also reset all of the throttle bodies (assume this is also a software callibration).
I've drive the car a few times now and its definately different at low rpm, when revved the engine picks up sharply and falls back to idle with no undershooting of the base idle speed or 'coughing' and has made pulling away easier and driving the car at low speed/rpm in 1st nicer. Engine is pulling well through the full rev range with no hesitations or surging.
So for those affected it might be worth asking your nearest dealer to try reprogramming the engine DME to the latest code and resetting the throttles. I hope this is a permanent fix and not something that drifts back after time. Phil Masek (Service Manager) at Cooper Chelmsford may be able to assist if they have further questions at to specifically what they did (above is what he told me).
Despite what I posted previously the 'reset' didn't quite sort it, it was a bit better but still had a tendancy to stumble if the throttle was tickled at idle which in turn could make it stall or bog down when pulling away.
Whilst in for warantee work I had the dealer look into it (Chelmsford, essex). On a short test drive their mechanic agreed something was not right but computer diagnostics did not show any sensor or fault codes to indicate a problem. BMW HQ gurus were consulted and suggested a update of the DME software/code would be the best course of action as thats simple to do. For those who don't speak BMW, the DME is the engine control computer. After flashing the DME they also reset all of the throttle bodies (assume this is also a software callibration).
I've drive the car a few times now and its definately different at low rpm, when revved the engine picks up sharply and falls back to idle with no undershooting of the base idle speed or 'coughing' and has made pulling away easier and driving the car at low speed/rpm in 1st nicer. Engine is pulling well through the full rev range with no hesitations or surging.
So for those affected it might be worth asking your nearest dealer to try reprogramming the engine DME to the latest code and resetting the throttles. I hope this is a permanent fix and not something that drifts back after time. Phil Masek (Service Manager) at Cooper Chelmsford may be able to assist if they have further questions at to specifically what they did (above is what he told me).