In cabin exhaust/gas smell???

FishinDVM · January 21, 2020

2014 Sierra 1500 5.3L V8 @97k and no CELs.

So, I dont smell it that often, mainly because I drive it all the time and probably am used to it, but anytime my wife and kids get in the car they immediately notice it. To the point of wanting to lower a window. It is worse at START UP, and also when idling for a while. You will not notice it while driving. The only time I pick up on it is right after remotely starting the vehicle, when I first open the door and get in. As I drive, it gradually goes away. Now I have smelled a view things in my day, hot burning oil, pure gasoline, exhaust, diff oil... to me, I think it smells like exhaust, possibly some mix of gas as a 2nd place option. I will admit though, that smell identification isnt exactly my strongest skill. Anyhow, I have changed oil, rear diff, transfer case, front diff, and trans pan fluids all within the last month. Didnt find any issues so far, and this smell has been there for a few months now.

I would like to know, otherthan a manifold leak or leak between the manifold and cats (which is what I'm going to check next), what else IT COULD BE??? I have sent some oil out to Blackstone to check for gas or coolant, my results are still pending. I also have changed the cabin air filter and didnt notice anything wrong. I plead ignorance on knowing where exactly the vehicle is pulling the cabin air in from however??? Does it come from the passenger side just below the wipers? Is there anything there I should be checking? I did notice a gap, on the passenger side, low, and behind the battery, between the side wall and what looks like firewall material... I added a picture... any thoughts would be appreciated... Thank you, Chris