CIS throttle body/ idle screw broke?

[mack6820]

Hey fellas! I've been fighting a weird hissing sound at around mid throttle under load. It only does it while driving so I cant find it sitting still. I think I've narrowed it down to the throttle body. So I removed the rubber boot cover, tightened the throttle body mount screws (got about 1/2 turn on each), inspected everything, then reinstalled the boot cover and air filter. Now the car won't hold an idle!
I tried adjusting the idle screw both ways and I'm getting nothing from it. Is it possible the idle screw is broken and causing these problems?
history, last year, I replaced the throttle body cause the vacuum tube broke off while removing the engine, this one is used from a fellow Pelican. I had the engine out and the tranny replaced during that time so It's hard to tell if I bought a bad throttle body or not. But when we reinstalled the engine is when the weird hissing sound came.

[Scott R]

Did you replace the o-ring between the TB and the airbox when you replaced it?

[mack6820]

I got it running again. I had to adjust the mixture alot to get it to hold an idle. The hissing noise is still there. I'm going to pull the TB off and check the o-ring when I get time. It still runs great, just this noise is driving me crazy.

[redstrosekNic]

Does the hissing continue all the time under mid throttle, or is it just when you first apply it? Is your air box modified at all? I have an aftermarket air box on my 75, and you can hear some hissing when you first hit the throttle. It is hard to hear unless you listen for it though, leading me to believe your noise is different.

[Scott R]

I just remembered that when my idle set screw was too far out it made that noise as well. Resetting the timing and the mixture, then doing the idle last put the air bypass screw back in the right place.