I have the exact same issue with my 15 suburban
90k miles
stock
did new plugs, new evap can
all new oem 02 sensors.
Nothing still smells rich at Cold AND Warmed up starts.
I have no codes but the trucks smells at any startup.
I was in a parking lot and another stock looking similar aged silverado smelled exactly the same way
I would thing more people would have this issue
its so bad we make sure to never idle it in close_ish areas and always run ac recycled
please help because other that that I love our suburban
thanks
