BMW 330i helicopter noise when idling, possibly related to fuel tank replacement on BMW 330i

Some BMW 330i owners report experiencing a "helicopter" noise coming from the engine while idling, particularly when the fuel level is low. This noise is often attributed to the fuel injection system, as service representatives have indicated that such sounds are common in these models. Additionally, customers have described a faint knocking or fluttering noise from inside the fuel tank, especially noticeable during low RPM or idle. Refilling the fuel tank can sometimes resolve this issue, as it has been frequently reported among F30 330i models with a 4-cylinder engine. Furthermore, problems with the air and fuel mixture, such as excessive air or dirty fuel injectors, may also lead to rough idling and contribute to the unusual "helicopter" sound. It is advisable for owners experiencing this noise to have a professional inspect the relevant components to identify and address any underlying issues.