2009 GTS, 110k Miles.
Pulling into work this morning I heard what sounds like a whining or whirling noise from the back of the car. It is pretty loud, similar to how low power steering fluid sounds. It happens at low speeds (could be at high speed but wouldn't be able to hear it over road noise). Here is the odd part, when I slow down say from 10 mph to 2 mph it keeps spinning and then slows down. Seems it is not entirely in sync with the amount of throttle.

It does not do it in park revving engine or idling. Is this something the fuel pump would do, though one would think it would do it in park then.

Any thoughts before I bring it in would be great. I normally tackle all things Porsche myself but am going out of town and need to get back and forth to airport.

 

I've never heard of anything like this. I like your fuel pump idea. As you slow down the vehicle, the pump would need to work less to keep up the fuel pressure. That might account for the lag.

Try getting up to a speed where you hear it and coasting in neutral.

 

Yeah good idea. A friend just called me and suggested the same thing. It's like the noise continues to happen as the drive shaft spins down. I'm guessing I could have rear diff issues? I'll try to on way home. Appreciate it.

 

 

I don't, but that is a good point. Was it controlled by an electric motor in 2009?

Anyway, here is an update. No noise on the way home or when I got home. Before I got out of it at work though I lowered it to loading mode and then put it back to sport height. I thought it could be a compressor pomp, though I know that sounds silly, I figured it was something simple I could do. I'll keep folks posted what I find out. Thanks all who replied.

 

 

Sounds like fuel pump to me. Put a can of SeaFoam into your next full tank of gas. It does wonders for lubricating the fuel distributor of the mechanical fuel injection system of older 928s and will do the same to your fuel pump, which may prolong its life by giving it some internal lubrication. It may not do it at initial idle because the lines were full and the pump primed when you opened the drivers door so it didn't need to work very hard when you first start it.

 

Thank you sir, always appreciate your suggestions. Will give it a go.