Acceleration rattle - Any ideas?

[Zaytar]

Hi Guys,

I've noticed a faint metallic rattle (appears to be coming from under the engine area) under hard acceleration. Almost as if the engine is struggling a little - which shouldn't be the case (its a 330i sport). Definitley doesn't sound like anything is loose e.g. exhaust. I'm sure I've experienced similar on weaker engined cars when they are being pushed - Just never heard before or expected on the 330.

Any experience of this or ideas? much appreciated.

[dodgyken]

High pitched? Low pitched? Engine bay? Further back? Left? Right?

Have you jacked her up and got underneath? Have you tried revving while standstill?

[Zaytar]

Low pitched, under engine bay (centre-ish), not had a look under car. Haven't a mechanical bone in my body unfortunately.

[RoRu]

Could be det or pinking as it's more commonly known, what fuel are you using?

[Zaytar]

BP Ultimate unleaded.

[beemer477]

could be the heat shield?

[RoRu]

BP Ultimate unleaded.


Although BP is a good fuel it's not unheard of for you to get a bad batch, especially SUL's as the additives seems to make them go "off" faster than normal unleaded petrol.

You could try filling up with a different brand fuel and see if the problem persists.

[Zaytar]

RoRu - Mate I think you've hit the nail on the head with the pinking. I've had a look into this, and I only noticed this sound when I switched from Optimax. I'm going to switch back and see whether the sound disappears in the coming weeks.

Cheers. :)

[RoRu]

If you've only just switched and you want to stay with BP then give it some time and the ECU adjust itself.