17 Tahoe Smell of Natural Gas / Propane Odor

[Jody Woody]

I know, I know, I've heard all of the "gas jokes". I have a 17 Tahoe 5.3 4wd w/ 53k miles. When the truck is warm and you stop at a red light you get an odor from the vents. If it vents are on re-circ you don't smell it, only on fresh air. It doesn't matter if a/c or heater. Been to dealer 3 times. They replaced the catalytic converters and that made no difference. Everyone that rides in it can smell it. It goes away when you take off. I'm not seeing any fluids underneath but I have to think its a small oil leak that is burning off.

Any ideas because none of the local GM or independent mechanics seem to have heard of this?

 

[Jody Woody]

I'm wondering if it could be some sort of emissions leak?

 

[wjburken]

I'm wondering if it could be some sort of emissions leak?

I would try and take it to an exhaust shop and have them take a peek at it.

 

[Fless]

Get a portable carbon monoxide (CO) detector and run it in the cab for a while, see if it alerts.

 

[Jody Woody]

Ill give it a shot.

 

[clintschleicher]

Did you ever find the cause for this? Having the exact same issue. Dealership
told me it was breaks, that was not the case.