I have an off idle whistle that is driving me insane. As soon as I hit the pedal, I hear an air sucking sound and a slight whistle which also happens at part throttle and goes away at full throttle.. I really dont think this is a vacuum leak because the engine runs fine otherwise. It sounds like the sound is coming from the stock throttle body. Any ideas on how to fix it?

 

My guess is that it is air rushing through the passage for the IAC. Not sure how you would go about addressing it.

Andrew

 

Misery loves company. I have the same whistle and unable to find it. Like you, I think that a vacuum leak has been ruled out because I replaced the gaskets and sprayed looking for leaks. Nobody else is reporting this whistle so whatever it is we appear to be in an elite group.

 

Ive heard that it can be normal, but not everyone has this problem. Its difficult to enjoy cruising with that sound. It almost makes me want to go back to an old fashioned big block. I have a feeling that it could be air passing through the throttle body blades.

 

It's not "normal." Some combinations of intake, TB, and intake tube probably has this happening. Neither my GTO, nor my Cougar have this. Post some pictures of the engine bay.

Andrew

 

Is it a GM IAC valve?

 

Mine is drive by wire. The whistle will get louder as the RPM increases in each gear. At idle and a bit above there is no whistle. At highway speeds there may be a small whistle but the wind noise on my '39 may be masking it.

 

Really common on non GM cars (Jeep) when the TB is bored and the IAC channel gets thinner..
Jeeps use a GM derived IAC valve, they whistle a lot.. When upsized.. Some guys have fixed it by
fiddling with the base gap on the throttle plate. (Close it and use a Hole in the butterfly ...)

 

Are you running the evap purge valve?

I had a VERY pronounced whistle at anything above 20 mph. Long story short, the charcoal canister started falling apart internally. Sent little bits of carbon sand through the vent line all the way up to the purge valve. Plugged the line solid. Once I cleared the line out the whistle went away.

Not sure how or why it whistles when it's plugged, but I promise you it did for me.

 

I'm not running a purge valve. Pic of the intake on my '39.

 

As far as I know, everything is stock GM, and I dont see a purge valve. Ill post up some pictures of the engine bay tonight when I get home from work.