Pretty new BMW owner. It is a 320D E90 registered in May 05. Done about 41,000 on the clock. Manual transmission, right hand drive, in the UK.
I'm having a problem and my BMW dealer (who has a pretty bad reputation), sadly, hasn't been able to resolve the issue.
Essentially, when accelerating to approximately 3000rpm the engine note will change and go off key - sort of higher pitch. This doesn't seem to be the clutch slipping as I can hold the rpm and the engine pitch stays. Interestingly, when trying to experiment and diagnose the issue, I don't really recall this happening with the a/c off. So, whilst the strange note was happening, I hit the a/c button and the strange engine note went away. I'm not sure if this is related.
The first attempt I took this into my BMW dealer they advised me that the vibration damper had warn and needed to be replaced - made sense to me - engine in general sounds less rattely not but sadly, the issue still happens daily.
I took it back again but as they couldn't replicate the issue this time they are handing it back to me.
The real pain is that it is intermittent, despite that it happens daily.
I'm a little at a loss & it concerns me as it sounds like something that could be causing damage to the engine.
Anybody have any ideas why my lovely 320D sounds like a teenage boy who's voice keeps breaking embarrassingly?
Many thanks for any advice. The car is covered by BMW under their used car warranty, but I'm thinking I may as well just take the cost on the chin and see if an independant will look at it