Underpowered Possible vacuum leak

[Angelo217]

2006 Chevrolet Tahoe 230k miles 5.3
Feels really sluggish and slow compared to my other 06 Tahoe with the same motor, feels like it has 50 less horsepower.

I hear a hissing noise when I give it a slight rev and let off it’ll hiss like it’s releasing pressure like a vacuum leak. I had my brother rev it up how I do and check under the hood.

The hissing noise sounds like it’s coming directly from the alternator, not sure if there are vacuum lines underneath that area hidden or not.

But if y’all could give me some pointers on why it might be so underpowered or maybe another place to look thanks

 

[Scottydoggs]

with all them miles a clogged cat is a possibility.

at idle you can spray some carb cleaner, flammable brake cleaner or the likes at the vac lines intake gasket areas, if the idle jumps up when you spray something, you found the leak area.

normally with a large vac leak that you can hear, the idle would be all choppy and kinda sound like you just put a huge cam in it with a 500 rpm surge.

you can also take the belt off, fire it up and see if the sound is gone as well. could be the alt is locking up, water pump, or even the ac compressor clutch ring is worn and making the noise. check the idler pulleys too. make sure they spin freely and smoothly with very little side to side play.

 

[Angelo217]

with all them miles a clogged cat is a possibility.

at idle you can spray some carb cleaner, flammable brake cleaner or the likes at the vac lines intake gasket areas, if the idle jumps up when you spray something, you found the leak area.

normally with a large vac leak that you can hear, the idle would be all choppy and kinda sound like you just put a huge cam in it with a 500 rpm surge.

you can also take the belt off, fire it up and see if the sound is gone as well. could be the alt is locking up, water pump, or even the ac compressor clutch ring is worn and making the noise. check the idler pulleys too. make sure they spin freely and smoothly with very little side to side play.

My other Tahoe had 70k more miles than mine, and she’s got the OG cats on it. I’ll try taking the belt off and using some carb cleaner when it cools down a little thanks!

 

[Angelo217]

here’s the vid of the noise it’s making.

 

[Doubeleive]

here’s the vid of the noise it’s making.

rig up a backpressure test and see what psi it has, just because it has more or less mileage than another does mean anything, mine has 170k and was clogged
you just need a gauge and a hose with a nozzle of some form attached to fit in the 02 sensor bung
you could probably just use a pipe fitting, hose, gauge, couple clamps.

https://www.napaonline.com/en/p/BK_7012005?cid=paidsearch_shopping_dcoe_google&campaign=GSC-Catch-All&campaign_id=6478877959&adgroup_id=79272987338&adtype=pla_with_promotion&gclid=Cj0KCQjw_sq2BhCUARIsAIVqmQtGqTcPWAvBVYr9qp9vXQG4prKjo1PHXrD9gDxuNPRjJluD57VTY9IaAj-nEALw_wcB&gclsrc=aw.ds&gad_source=1

 

[Fless]

That whine is not normal, and sounds like a pulley or tensioner issue with one of the belt paths. Power steering have enough fluid in it?

 

[Angelo217]

rig up a backpressure test and see what psi it has, just because it has more or less mileage than another does mean anything, mine has 170k and was clogged
you just need a gauge and a hose with a nozzle of some form attached to fit in the 02 sensor bung
you could probably just use a pipe fitting, hose, gauge, couple clamps.

https://www.napaonline.com/en/p/BK_7012005?cid=paidsearch_shopping_dcoe_google&campaign=GSC-Catch-All&campaign_id=6478877959&adgroup_id=79272987338&adtype=pla_with_promotion&gclid=Cj0KCQjw_sq2BhCUARIsAIVqmQtGqTcPWAvBVYr9qp9vXQG4prKjo1PHXrD9gDxuNPRjJluD57VTY9IaAj-nEALw_wcB&gclsrc=aw.ds&gad_source=1

Where would I hook that gauge up to and what would this tell me/ what psi reading should suggest normal range

 

[Angelo217]

That whine is not normal, and sounds like a pulley or tensioner issue with one of the belt paths. Power steering have enough fluid in it?

Nah the whine is fine I know these all whine im just pointing out the sound of pressure/ air releasing escaping whistling noise when I let off the accelerator it’s most prominent. Like a vacuum leak. Thinking that has to do with why this thing feels so sluggish.

 

[Angelo217]

Also will mention I get an intermittent code for a fuel tank pressure sensor which for some reason makes my ac act funny. Makes the compressor not kick on, and or it’ll be turning on and off every few minutes. Seems unrelated, just thought I should mention just incase but these are my codes
P0651 and a P0452

 

[Fless]

Nah the whine is fine I know these all whine ...

Not so; a lot of them DON'T whine. Mine did a little (not as much as yours) before the power steering pump for the hydroboost was replaced. Now it doesn't.

 

[Scottydoggs]

your ac system is low. when low the compressor comes on and off.

sounds like a idler chirp. pull the belt, hand spin everything. if you dont see a belt diagram under the hood some where, take a pic of the belt on the truck. nothing like trying to figure out that puzzle lol

 

[Doubeleive]

Where would I hook that gauge up to and what would this tell me/ what psi reading should suggest normal range

you would need to check to verify psi for your vehicle mine was supposed to be 2.5psi max, it was reading 5 at idle and 10 with throttle
but the test is done thru the 02 sensor bung, (pre-cat)

 

[Angelo217]

your ac system is low. when low the compressor comes on and off.

sounds like a idler chirp. pull the belt, hand spin everything. if you dont see a belt diagram under the hood some where, take a pic of the belt on the truck. nothing like trying to figure out that puzzle lol

I know these gauges usually aren’t trusted but it actually said the system was slightly overfilled, one of those autozone cans. It’s just strange to me how the ac only starts acting up immediately when the check engine light comes on for the FTPS.

The ac will work fine for a straight month, and then check engine will come on and it acts up.

 

[Angelo217]

your ac system is low. when low the compressor comes on and off.

sounds like a idler chirp. pull the belt, hand spin everything. if you dont see a belt diagram under the hood some where, take a pic of the belt on the truck. nothing like trying to figure out that puzzle lol

Idler chirp would cause that whistling noise?

And I recently had the belt off doing the water pump 3 weeks ago, all them bearings up front sounded fine

 

[Doubeleive]

Idler chirp would cause that whistling noise?

And I recently had the belt off doing the water pump 3 weeks ago, all them bearings up front sounded fine

if the sound is not there with the belts off then it is something bolted on. use a stethascope