Well...It's definitely doing more than just humming. It sounds like a little electric motor with a gear, trying to catch another gear.

There's also the fact, that once I move the throttle, the noise goes away (I am assuming the gear got caught).

I am thinking that the throttle plate is not closed all the way, and that at the same time, the engine is getting extra fuel.
Cold starts are fine, drive off is good for about 20 seconds, then I get a hesitation/stumble for a moment or two. Warm/Hot starts are no longer instant or near instant... I have to resort to stepping on the gas a little to get it to start.
Since my discovery of the noise, and how to make it "go away" by stepping on the pedal prior to engaging the starter, I have been able to get satisfactory Warm/Hot starts.

I don't suppose there are any user servicable parts inside, are there? (provided I can extricate the thing)

Thanks!

-Larry

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It is a truism that almost any sect, cult, or religion will legislate its creed into law if it acquires the political power to do so. Robert A. Heinlein


09 Jetta TDI
1985 300D