I had this problem a while back and it had gone away but its come back now . Sometimes (not always or even at regular intervals) when changing down to 2nd coming up to a roundabout or junction the whole engine appears to cut out for a very brief period and then straight back on and running fine. I've not noticed it in any other gear. Everything else works fine. Smooth idle, starts first time, pulls well, does about 25mpg normal 30 on a run. Just wondered it anyone had any ideas.
2004 Manual Roadster.

 

I had something similar happen with my previous car a ML320 Mercedes which has the same engine we have. when coming up to a stop the engine would almost die but not quite. As time went by it finally started to die when I came to a stop light. It turned out to be the crank position sensor.

 

I was wondering if that might be it but it onlly seems to happen in second so thought maybe some sort of sensor on the transmission?

 

Only sensor on the 6 speed is to notify the ECM when your in reverse so revs are limited when backing up!! Forget what that r p m is limited to but 4000 comes to mind right now.

 

Probably not that then