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Discussion Starter #1
Had this posted in another section with not much response.
This is on my 987.2 CS. Have this odd sound that comes and goes. When idling you can hear it come and go. Give it a little throttle and it goes away but then comes back as the rpm's come down. No codes and car drives fine. I can't tell for the life of me if it is coming from the engine compartment or under dash. Not HVAC related, no changes with temp or fan speed changes. I have used my mechanics stethoscope and don't hear it in the block. It does transmit through the seat track, so maybe something radiating from under car??
 

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Does it matter if the engine is cold or hot?

No idea what that is. First thought was a vacuum leak - but you'd probably have other symptoms. Check fluid levels, especially power steering fluid. Just a reminder the PS reservoir dipstick has two markings, but they are hot & cold levels, not min/max.

Next thing to try is to remove the serpentine belt and spin all the pulleys - including the idler. Listen and feel for any sounds or friction/looseness. Then run the engine for a short time without the belt and see if the noise is gone. Even if it is still present, there will be much less ambient noise which may make it easier to isolate the sound.
 

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Okay, I have found the source, It is coming from the fuel pump and radiating through the hard lines. Car is running fine, no codes. Do i preemptively replace it or drive it and see if it gets better or worse? My car has no outstanding recalls so I do not believe it is part of the fuel pump campaign. Could a bad tank of gas cause it?
 

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I'm interested in the fact that the sound comes and goes depending on engine rpm. I wonder if your alternator is putting out sufficient voltage at idle? You might check that, and check the battery too. If the voltage is too low the pump may be struggling.

I don't think quality of gas would cause this, unless there was actual debris in the tank blocking the pump inlet.
 

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Discussion Starter #5
2010 CS, new to me but we'll maintained with 35k miles. Likely not debris. Good suggestion to check voltage.
 
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