Chazcamp

I have enjoyed this community and my early 993.

I have scoured this forum and may not have a problem at all but wanted advice.

I hear a hum or buzz type noise and can feel the vibration from the upper central engine bay. This is heard with ignition on before car is started. It’s not the blower fan. Is there another fan that runs when ignition is on? Is there some other electric part/pump that makes this noise. Is it normal?

Thanks for any input!

notabot

AC compressor?

Chazcamp

Noise is regardless of AC settings, heard constantly with heat on too, engine off. Not AC compression, I don’t think... i hear the noise higher and centrally over engine even when it’s not spinning

it’s an electrical hum unless there is another fan that’s always on somewhere. Just wonder if something is about to go out or if it’s normal.

pp000830

Hi Chaz,
Sounds like the fuel pump running. The sound can seem to be coming from under the engine due to sound conduction through the body
Also, the idle valve on top of the engine vibrates when active in the center above the engine and if its rubber mount is out of position so the metal body of it touches the metal intake manifold I suspect it could be quite loud.
Andy

IainM

SAI pump?

pp000830

Probably not the SAI pump as it runs for only a few moments on a cold start and makes a sort of a muffled jet engine sound if there is an air leak.
Andy

Twilightblue28A

I'm with Andy- fuel pump.

Chazcamp

I think it’s the idle valve on top of the engine. Is this supposed to run when the switch is in the second position but the engine isn’t on yet?