Was cruising on interstate, approx 2800 rpm the other day when I started to get a loud screaching sound from engine. After 15-20 seconds it went away. 20-30 min later back it came. Went on for the next hour or so. Noticed that it only happens when in vacume, any boost and it will instantly go away, back to vacume and it will return.
Checked all hoses when i got home but determined that it is coming from under intake manifold. Its getting worse in frequency and duration and happens in all gears when in vacume. Sounds like something is resonating or vibrating
Anyone have any ideas?
Thanks

 

Is it a metal on metal sound, or more of a wind blowing sound?

Does it happen when the car is cold, hot, or both?

I had a strange sound coming from one of the hose of the air pump. Only happened when the car warmed up and the hoses were warm. Of course mine only happen when the air pump was engaged, so going WOT it would shut off when the air pump wasn't needed.

Replaced the hose, but it was damn annoying and embarrassing until it was found.

 

Jamie, have you recently performed the hose replacement? Or have you removed your intake manifold? I'd check your AWS system. There is a small gasket which connects the intake manifold and the AWS, if not aligned this can cause this metallic fluttering sound. I'm not sure this is your problem, just a guess.

eric

 

check your ACV

 

Thanks for the input guys, happens when car is both hot and cold, sounds like something vibrating but really more of a resonating sound, and its loud.. And yes it started on my trip back from getting work done at KDR, they had the intake off. I am NOT flaming Dave, I think he does great work, just trying to see if I can figure out what it is and fix myself, want to avoid the 6 hr one way trip to have him look at it