View Single Post
      06-03-2009, 10:22 AM   #17
KoPe
New Member
0

 
Drives: e90
Join Date: Apr 2007
Location: finland


Posts: 8
iTrader: (0)

N-series motors have a pump that pumps air into exhaust manifold when idling. This is for emission control. That keeps a knocking like sound that sometimes may appear like "tractor" or diesel sound.