The Unexplainable, Unresolved issue an expert LS builder and Dealership can't figure out

[swathdiver]

So to revive this old Thread, here is an update for anyone interested.
I took my suburban to the GM expert independent shop.
The did not address my concern, they sold me a Direct Injection cleaning and Injectors cleaning.
Not that I mind, as I wanted to do the direct injection cleaning anyways.
This did not change any of the smell.

To recap if some of you don't want to go back to all the different pages and bogus info I was given or thought it could be, this is where I stand on this of of right now:

At every start upt, cold or fully warmed up engine: the truck rear tailpipe smells super rich.
as in raw gas strong smell.

I am taking the truck to an actual emission place who is going to hook up HP tuner or some diagnostic to look at the tables while starting it tomorrow morning

Recently, I had a 19 loaner with the 5.3 and I could have sworn that that brand new unti also does the same thing, smells really rich at startup and idling.

My particular smell stop once I get going and then stop.


Maybe its something GM designed (poorly) into the truck, my truck is all stock with no lights on the dash, everything indicate that I am running in good condition.

I will update with that shop finding.

Like the carburetor days with chokes, the engines run rich at start up to get up to temperature quickly.

 

[AZCreeker]

Like the carburetor days with chokes, the engines run rich at start up to get up to temperature quickly.

its unlike any other truck / car I have. Its way way too foul smelling and way too much, it also doesn't even after starting the car for 5 minutes. What you are describing usually, I can smell a bit of a difference. on mine its bad.
smells way to much like pure unspent gasoline. I wish I could put a scratchOsmell link like the videos from the 80's had sometimes their smell board to go with it.

 

[swathdiver]

its unlike any other truck / car I have. Its way way too foul smelling and way too much, it also doesn't even after starting the car for 5 minutes. What you are describing usually, I can smell a bit of a difference. on mine its bad.
smells way to much like pure unspent gasoline. I wish I could put a scratchOsmell link like the videos from the 80's had sometimes their smell board to go with it.

This just occurred to me, does it smell like some critter crawled up the tailpipe and died? Hot exhaust cooking his dead carcass and stinking the place up?

 

[AZCreeker]

This just occurred to me, does it smell like some critter crawled up the tailpipe and died? Hot exhaust cooking his dead carcass and stinking the place up?

LOL! thanks but nope just raw raw gas.

 

[swathdiver]

LOL! thanks but nope just raw raw gas.

Well, I'm going to pick a stuck/leaky injector for $500 Alex...

 

[Rocket Man]

So to revive this old Thread, here is an update for anyone interested.
I took my suburban to the GM expert independent shop.
The did not address my concern, they sold me a Direct Injection cleaning and Injectors cleaning.
Not that I mind, as I wanted to do the direct injection cleaning anyways.
This did not change any of the smell.

To recap if some of you don't want to go back to all the different pages and bogus info I was given or thought it could be, this is where I stand on this of of right now:

At every start upt, cold or fully warmed up engine: the truck rear tailpipe smells super rich.
as in raw gas strong smell.

I am taking the truck to an actual emission place who is going to hook up HP tuner or some diagnostic to look at the tables while starting it tomorrow morning

Recently, I had a 19 loaner with the 5.3 and I could have sworn that that brand new unti also does the same thing, smells really rich at startup and idling.

My particular smell stop once I get going and then stop.


Maybe its something GM designed (poorly) into the truck, my truck is all stock with no lights on the dash, everything indicate that I am running in good condition.

I will update with that shop finding.

I agree with @swathdiver that it might be an injector issue. Nothing else really makes sense. How your gas mileage out of curiosity?

 

[91RS]

If a 2019 loaner does the same thing, it sounds like it's normal to me. Newer vehicles do run rich on a cold startup to get the cats heated up as fast as possible (where they are the most efficient) compared to older vehicles.

 

[Richard Blakely]

Thanks that is some precise things for me to check. I will let you know.

Do you experience any wetness under rear floor mats? My 05 suburban had that. Turned out to be leaking heater core. They’re fun to replace!

 

[AZCreeker]

nope. its 100% at the tail pipe. I am going to have an exmission shop hook up a dignostic tool and look at the various table and finally try to get this thing dialed in

 

[Doubeleive]

Sounds like normal GM tailpipe smell to me, of course I don't make a habit of sticking my nose in the tailpipe but I have smelled similar tailpipe odors before, doesn't seem like anything out of the ordinary.