h3 2007 3.7 Does anyone know what the smell is that comes through the vents when you get on the highway and accelerate fast. This seems to happen at High RPMs. Is this a normal thing?

 

 

No, not normal, but probably is a leaking exhaust manifold. Mine leaks, and I get the occasional smell at idle when standing still.
I'll eventually replace it, but I'm not looking forward to the job, and thus procrastinating on it.

 

I took several deep whiffs, can't smell it from here.

Coolant leaks smell sweet, exhaust is like weak rotten eggs/sulfur, oil leaks cause smoke and a a burnt oil smell (think of burning rubber), HVAC mold and moisture not draining properly smells like a musty basement, Trans slippage and heat smells like burning paper, and dragging brakes/excessive brake wear smell like burning fabric. Your nose is the diagnostic tool for what to closely inspect as Grandad used to say.

 

ac refrigerant has an odd smell hard to describe but kind of like new band-aid smell, leaking evaporator maybe?