terry.davis1

As the title says. Part of my head tells me that it has always done this, but it's seeming to annoy me more and more lately...so I'm thinking something is up.
I have a whistling noise that I can hear pretty loudly (especially when the windows are down) that is coming from the engine bay. It seems to be throttle dependent and only occurs when my boost gauge reads between 5 In. Hg and about 3 PSI. I did change the boost gauge to an Autometer manual last year as my stock one had given up about a year before that. I had my wife rev the motor, but you can't hold the idle up and keep the boost pressure up when there is no load on the motor to diagnose it easily. Running down the road, you can hold the boost and hear the thing whistling profusely. It sounds much like a vacuum leak, but it will still make full boost with no issues, and is not present at idle. When she was revving it, it sounded like it was coming from the vicinity of the actuator valve. This makes me think that the actuator is bad, but I hate to buy a new one and find out it wasn't it.

Anybody have any thoughts that know more about this car than I do?

05Slowline

iTrader: (2)

if you're stock downpipe your dp prob cracked at the accordion flange, you can't see it it'll be a hairline crack but it's there. irritated me for months till i bought an aftermarket

terry.davis1

I doubt it's an exhaust leak. I cracked the flange on my Grand Am GT a few years ago...was hella loud. An exhaust leak will be heard at all throttle positions. And it's not coming from "under" the car so to speak. It's definitely top side near the S/C

MP Cobalt

iTrader: (4)

check the bypass valve

terry.davis1

What exactly should I be checking for?

MP Cobalt

iTrader: (4)

a leak or area that isn't sealing. It's like a 30 dollar fix on zzp site. it's most likely the bypass valve if it makes the noise under throttle

06cobalt racer

iTrader: (11)

mine does the exact same thing

05Slowline

iTrader: (2)

not necessarily, i only heard mine under boost, and it was a hiss, was just a pinhole crack but whatever you say

Coblasts

This could be your answer

#PIP4392: Whistle Noise From Throttle Body Area At Or Near Idle - keywords engine gasket LE5 intake manifols orifice plate

Condition/Concern:

Some customers may report a whistle noise that is heard at or near idle. Upon inspection, the technician should be able to isolate the noise to the throttle body area of the engine. If the noise is compared with others, it may also be determined that this is a noise characteristic of the engine.
Recommendation/Instructions:

If the SI diagnostics do not isolate the root cause of this noise, perform the following steps to improve this noise characteristic:

Follow the Intake Manifold Replacement Procedure in SI to remove the intake manifold.
Remove the PCV orifice plate that is between the #2 and #3 intake manifold runners.
Plug the PCV orifice by placing a small amount of epoxy on both sides of the PCV orifice plate as shown below in Step 4.
Use a #51 (.067" / 1.7 mm) drill bit to drill a new orifice in the location shown below.

06cobalt racer

iTrader: (11)

thats for a le5 though. also he said its around zero boost

terry.davis1

This

thecutlip

I know this thread is kind of old, but I have the exact same problem. Did you ever figure out what it was? I know mine isnt the downpipe, because I just put a zzp one on last night.

Manopka

Im gunna rebump this instead of making a new thread. i have this same problem and have no idea what it is. It only occurs at a specific throttle position.

Imagine the pedal has 5 positions where #5 is all the way to the floor and #1 is not being pressed at all. The whistle only occurs around #2ish. If I let go of a little gas it stops and if I press it a little more it stops.

I know one of you guys will say "just dont press it to the #2 spot" but thats just avoiding the issue and #2 happens to be my daily driving go to position.

terry.davis1

If yours is supercharged I would be willing to bet it's the same issue that I'm having. I'm pretty sure that it's a torn diaphragm in the boost bypass actuator.

GM p/n 12591349 (GMPartsDirect.com)

I haven't gotten around to ordering/replacing mine yet. I've kicked around the idea in the last few weeks of trading this thing in

Manopka

fuhhhhhh. $135 to get rid of a whistle? no thanks.

tazh3294

Were y'all experiencing a noticeable loss in power?