Intake manifold leak?

[Defo26]

[Defo26]

2015 GMC 1500 5.3L 

noise is coming from what sounds like under the throttle body slightly to the right. Fuel mileage has dropped, power has dropped, no check engine lights. Very loud when under load. Strong smells of combustion fumes if standing over throttle body. 

 

Edited December 10, 2021 by Defo26

[newdude]

Wow.  Surprised there isn't any codes like lean codes.

 

I'd be looking for cracks on the intake.  It could be just a bad gasket, but I don't think it'd be that loud.  

[rbdjr]

sounds like broken valve spring or cam has flattened out a lobe

Edited December 10, 2021 by rbdjr

[CamGTP]

I'd be removing the intake to get a better look at it.

[Defo26]

Thanks guys I’m going to get it in the garage tomorrow.

[Jdenney34]

Was you able to identify your issue. My son has a 2014 Sierra with a 6.2 and it is making the same noise. 

[Lilsoggy74]

Was this issue ever solved? 
having same issue in a 2015 chevy tahoe 5.3

 

any help would be much appreciated 

[Jose Soto]

Old thread I know. But you found out the issue? I did a 5.3 L83 to my 2003 silverado and it has the same exact sound but in the back of manifold. 

[justin hutchinson]

Did you figure out the problem? 

[Alpe]

What was the problem and how did you fix it???