whistling throttle body

[Duck]

I have a '91 L-98 coupe with AT that has a high pitched, but low volume, shrill "whistle" coming from the throttle body area of the engine compartment. It is usually present at idle, and gets higher pitched with increasing rpm's to about 1000 rpm or so, then goes away. It comes back when the engine is at a relatively steady rpm. It can be heard from inside the car, but is not really noticeable at speed, but can be heard easily at idle.
Anybody have any idea what might cause this noise? I have not yet looked into this in any detail, other than to figure aut what area of the engine it's coming from. The car runs fine otherwise, no driveability issues at all!

 

[Ken]

I don't know what else to say except that it sounds like you might have a leak around the air filter box or something. A "whistling sound" is a pretty vague description of the problem, if indeed it is a problem. Are you seeing any codes?

 

[vetteboy86]

What about a bad gasket between the TB and the Plenum? Could there be a crack in the air hose between the TB and the MAF?


craig

 

[WhalePirot]

You can search for air leaks with WD-40 spray and good ears.

The spray fills the opening for a second and changes the sound and/or the idle.

 

[Ken]

... and good ears.

... Or a stethoscope made from a piece of vacuum hose.

 

[Seahorse51]

91's don't have MAF's.