Whistling noise above idle

[de3jr88]

Greetings. I have not posted in a long while, but I am looking for some expert technical opinions. 2003 Envoy SLT I6 4x4 4.10 rear end. This was my wifes daily driver for nearly 10 years but is now mine. I had noticed about a year ago that there is a low 'whistling noise' under throttle or when cruising. Cant hear it when windows up or sunroof closed. When windows down or sunroof open you can hear it. When rolling up to stop signs or lights, just before engine drops to idle, it goes away. Does not change tone under acceleration, but is louder during gear changes. Is no different with AC or heater on. I can hear it more from passenger side, but parked cars or roadside obstructions are closer and sound rebounds faster. Now that I drive it every day, I notice it more. Have not noticed any performance difference, or fuel economy.

I dont think it is a pully or a moving part on the engine due to the sound not changing in tone under throttle. Brakes are good, bearings are good.

Any thoughts?

 

[Capote]

Is it a whistling like a vacuum leak possibly? If so, have you checked for any vacuum leaks?

 

[de3jr88]

It could be, that is more what it sounds like. Its not a window or door seal for sure. I have checked hoses under the hood and they appear ok. Are there vacuum lines under the frame?

 

[Capote]

There's an Secondary Air Injection Pump under the frame on the drivers side. A lot of times these can crack and corrode.

 

[de3jr88]

Sounds like I have more investigating to do. Hopefully i can recreate the noise while parked. Thanks for your input!

 

[Capote]

No problem, if anything have someone give the rig some gas as you investigate around the engine bay and underneath.

 

[de3jr88]

That will be tomorrow's mission if possible.

 

[Wooluf1952]

The 2003 doesn't have the SAI. That started in the 2004, IIRC.

 

[Capote]

The 2003 doesn't have the SAI. That started in the 2004, IIRC.

Hmm is that so? One other difference learned now between '02-'03's vs '04 and up.

 

[jsheahawk]

Any codes?

 

[de3jr88]

Nope no codes, no CEL. There is a box of some sort with hoses in and out mounted on the frame under the driver seat area, just ahead of the fuel filter. I thought that was the secondary air injector?

 

[Capote]

Nope no codes, no CEL. There is a box of some sort with hoses in and out mounted on the frame under the driver seat area, just ahead of the fuel filter. I thought that was the secondary air injector?

That's it