Quote:
Originally Posted by M&M
OK, so let's think about this for a moment. Correct me if I'm wrong but the wastegate is fully open at idle. When you accelerate you need boost. So the vacuum pulls the wastegate shut instantly when you accelerate. Then you let off or decelerate, there is no more need for boost. So the vaccum is released & the wastegates go back to fully open. Also when you idle there is no need for boost & they are open. The problem seems to be when they are in this position. Maybe the wastegate "door" is rattling against something. But I'm just thinking out loud here.
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Actually, suposedly the door is closed or partly closed at least at idle to improve emissions. But as far as it being the wastegate door rattling, that's not exactly a new concept since that is common knowledge and exactly what BMW already told us it is in the TSB linked in this thread
The theory being discussed here is that it is not in fact the door rattling but rather the loose actuator arm mechanism.