Loud hum from engine bay
 

Hi, I'm hoping someone can help me figure out what's wrong with my car.

I recently changed my power steering pump, with required removal of a lot of things in the engine bay. After I installed everything, I'm now getting a loud hum, really more like a constant tone from the engine bay. Is hard to pin point the exact location (I need to find a hose somewhere). The sound appears when accessory power is applied, and removing fuse B8 (think that's right) stops the sound. It's a tone with a frequency of 1800 Hz with a strong second harmonic at 3600 Hz.

The fuse description says it's the alarm, but I though that was under the hood.

Attached is the spectrogram (I couldn't upload a video), and a picture of the fuse that stops the sound when removed.

Thanks in advance!
Bryan

It seems fuse B8 is for the alarm, ECU and Tiptronic control. Can the humming be coming from the idle control valve oscillating between two positions? And it just stops because you disconnect the DME?

Yes, so it's definitely something in the throttle. I took the throttle off and the buzzing is coming from the butterfly. If I press on the butterfly with my fingers, it goes away.

Does this mean I need a new throttle body? Has anyone seen this before, and is there a common fix, like taking apart the throttle and cleaning something?

I have a 2002 so apparently it doesn't have an idle control valve.

I guess this is a sign that I should upgrade to the bigger throttle 😆!

Oh, it's the throttle body's actuator then. Probably you messed with its cable while working around the pump, shorted somehow or similar. Inspect the wiring harness and all cables in the surroundings of the area you have worked at.

A thorough cleaning with some brake cleaner seemed to work fine. Thanks for the help!