Originally Posted by Tiago@VRSF
Our shop 335i has this same problem & has had it since 20k miles.
Could be the injectors opening/closing, valve tap, lifter tick, exhaust leak. Could be quite a few things. Most people don't notice it on their own car because they never have the hood open when the engine is on. I'm guessing the sound is consistent with RPM?
it only occurs at idle, so when the rpms go up or you rev it the sound stops, upon declining and returning to idle the sound will start again. car has new injectors but thats interetsing that your shop car has had this as well. you can hear the sound with the hood closed.
e92 335i sport[/b] 2 GO
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