Crispy

I recently noticed that when I shut engine off, and still have power to the car I hear a strange humming noise comming from the top of the engine. It almost sounds like the resonance you here after hitting two pans together. The noise is not heard every time. And it does not dissapate until I flip the ignition off completly.
The car is a 93 coupe with a B20 Obd1 pr3 ecu. mostly stock engine.
I was told it might be a sensor by a friend.

StylishDOHC

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Crispy &raquo;</TD></TR><TR><TD CLASS="quote">
I was told it might be a sensor by a friend.</TD></TR></TABLE>

lol

Crispy

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by StylishDOHC &raquo;</TD></TR><TR><TD CLASS="quote">

lol</TD></TR></TABLE>

Wow, helpful.

Thats what I thought too though. But I cant for the life of me figure out what is making that noise. It does not seem to affect how the engine runs, (It's not streetable) The only thing I am sure of is that it's comming from the top of the engine, possibly around the intake manifold. The noise is present when the engine is off. Cutting power to the engine harness makes it stop, and if I am to turn the power back on it will not make the noise again unless I start the engine.
And to be more descriptive of the sound, It sounds like a low pitched steady humm that resonates all around. (Why I cant figure out where it's comming from) Oh and I just remembered something importand, Opening the throttlebody Will change the pitch of the sound.

Max Kling

Try unplugging the IACV when its making the noise.

sageuvagony

I've though tabout the same noise I have... Open and close the throttle with ignition on but engine off.. The sound will change slightly. Touch the IACV and you'll feel the vibration from the hummmmm.. I always wondered the same. Any reason why it does that?

sageuvagony

Crap.. I didn't read the whole post then noticed you already mentioned opening and closing the throttle lol...

Crispy

Yup, it is comming from the IACV. So I guess the question now, is why is it doing that. and other than sounding wierd, is this a bad thing? The obvious answer would be just to replace it, but is there something that causes this to happen?

Max Kling

Its kinda a common thing.

With the ignition off unplug it and check to see if it is still getting voltage which it shouldn't be. If its getting voltage with the switch off its wiring related. Thats about the only thing I could think of. Mine use to make weird noises sometimes, it would click real fast and sounded like a machine gun on occasions when I was trying to rewire it.