Exhaust/vacuum leak?

[jyi786]

My truck is a 2012 Yukon Denali XL. Recently, I started noticing a very loud hissing sound emanating from around the bottom driver's side of the truck. It sounds either like a vacuum or exhaust leak of some kind. The noise is most prominent by the driver's wheel area. Just stand there and you can hear it.

Another thing I noticed is a difference in the way the truck starts when starting cold. My truck normally starts very strongly, but as of recent, it will slightly "choke" when starting, then rev up to normal. I wonder if these two issues are correlated?

I also *thought* I notice the truck struggling to pull when I hit the throttle, but right now it feels more like placebo effect than anything.

I have had direct experience with a catalytic converter failing. It failed on my Olds 88. It caused the car to be unable to shift to second. I have no such issues with my truck, so I'm not sure if that's it.

What do you all think? Is this maybe nothing and I'm just being a bit paranoid?

 

[kbuskill]

You didn't specify front or rear wheel well.

I would slide under the truck and see if you can locate the source of the sound.

 

[jyi786]

You didn't specify front or rear wheel well.

I would slide under the truck and see if you can locate the source of the sound.

Oh my bad. I thought that saying "driver's wheel well" indicated that it was up front.

 

[kbuskill]

Oh my bad. I thought that saying "driver's wheel well" indicated that it was up front.

Drivers side has 2 wheel wells... lol

 

[jyi786]

Drivers side has 2 wheel wells... lol

Lol

So yeah, I can hear it the most when I stand right outside the driver's side door up front.

 

[kbuskill]

I would slide under and take a peek and have a listen. Could be fuel pressure related but I would think you would smell gas.

 

[denalianyone]

Probably cat on the left babj


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[swathdiver]

A bad cat should throw a code P0420 or P0430 if you have working lower O2 sensors. Mine does everyday! Don't think an exhaust leak, unless you blew a header gassket would cause the motor to stumble, that would more likely be vacuum related an intake gasket or such.

 

[denalianyone]

A bad cat should throw a code P0420 or P0430 if you have working lower O2 sensors. Mine does everyday! Don't think an exhaust leak, unless you blew a header gassket would cause the motor to stumble, that would more likely be vacuum related an intake gasket or such.

It should as you say but a rattling cat can sometimes not throw a code. I had that experience.


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[jyi786]

Yeah, I'm not hearing any rattling can sounds, the truck doesn't really stumble, nothing that I can discern except the hissing and the slight choke on start (in 20 degree weather or so). And no codes are being thrown either.

I don't know if this is related, but sometimes, after a long drive, when I get out of the truck and it's still running, the exhaust smells a bit foul.