I've got a stumper for everyone.
I recently noticed that my 2006 A3 2.0t DSG (73k miles) is making a strange rattle like noise when applying specific amounts of light throttle. It's most noticeable when cruising at highway speeds (its pretty much continuous).
- It is not RPM dependent.
- It is not gear dependent. Although it doesn't really occur in 1st or 2nd gear. In 6th gear I did notice that at high speeds (90+) that it will still lightly make the noise even at full throttle.
- The sound is the same whenever it makes the noise. The only thing that seems to affect it is engine load/throttle. It does vary in frequency and pitch a bit at different loads
- I've pulled apart most of the top of the engine bay looking for potential rattles. It appears to be more internal related
- Oil change was performed to ensure it was not related
- No engine codes
- I recently had the fuel pump cam follower replaced and suspected that. I went back to the shop and they removed it and checked it again to ensure that was not making the noise.
- Same shop checked the PCV system for issues, none found
- I did the fuel line rattle fix to ensure that was not it. It did fix the idle fuel line rattle at least.
- I suspected a potential by-pass valve issue and pulled the n75 valve connector to see if it had any effect. None.
- I suspected a potential wastegate issue and pulled the n279 valve connector. It still made the noise, but it did seem to change the behavior a little bit. It seemed to take a bit more throttle input to make the noise happen. So this could be related in some way.
- I can't make it happen while the car is not in motion through revving in neutral or by brake torquing the motor.
That's about all I've got on this thing. It's driving me nuts. I'm going to try bringing it by the dealer this week. My usual independent shop had zero luck figuring it out.
HELP! I'd welcome any and all thoughts.