White98

We have started to experience something strange in our 98. You can be driving at slower speeds or just sitting at a light and you'll hear what sounds like a loud sucking noise. It will initially increase or hold the RPMs but if you don't goose or rev the engine it will die. Have noticed also that if you goose the throttle it will hold the RPMs up for a little while then drop them back to normal. Just seems to hold it longer than normal.
I have checked the cold air system for air leaks and everything is tight. This was happening before I installed the cold air system...hoped it would fix the problem.
Looking for ideas. Seems to be happening more and more. Could it be the throttle body and the butterfly is vibrating?
Thanks for any ideas.

Evan02

Sounds like maybe a vacuum leak somewhere. A good place to start would probably be to turn the car on and pop the hood and see if you can find the general area of where its coming from and check all your vacuum lines.

White98

Looked at that thoroughly. This noise almost reminds me of a honking noise. Not a beep beep sound but a low horn blowing. I thought it was the air cleaner that had fallen to the side or something and some air was getting by but not enough. Replaced that and still the noise. Weird thing is when it happens it holds the RPM steady for a while then will stall the engine. I started thinking I might have a butterfly that is hanging up somehow.

xx10Gt

Pop the hood and spray brake clean/parts cleaner very lightly around your vacuum lines. If the idle changes youve got a vacuum leak. Just a quick spray here and there should tell you

Camster

Wild guess. IAC?

White98

Camster, I'm beginning to lean in this direction. Not really sure how the IAC works but everything is pointing in that direction.
Thank you for the tip.

WhiteFoxGT

'IAC valve, when they go bad they can "hoot"

White98

Changed out the IAC valve...no more noise or idle problems. Thank you all for the advice.