BMW 3-Series (E90 E92) Forum - View Single Post

KoPe · 06-03-2009, 10:22 AM

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.

06-03-2009, 10:22 AM	#17
KoPe New Member 2 Rep 8 Posts Drives: e90 Join Date: Apr 2007 Location: finland 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.
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