Anyone know how the “recirc” mode works? I’m getting an oily smell in the truck, goes away when I move to the fresh air setting. I don’t have any oil or exhaust leaks, brand new PCV as well. It’s a fairly strong odor, can’t figure it out.

 

No smell under the hood? I'd say either oil or tranny fluid is dripping onto the exhaust and burning off before it hits the ground or you have a cylinder issue. Have you checked the plugs?

 

"Oily smell" doesn't necessarily mean actual oil. All kind of stuff can end up behind the dash. Who knows what it will smell like after sitting in the sun for a few weeks.

Here's a schematic of the ducting. http://web.archive.org/web/201102052...g/25heater.pdf I'd get access to the blower motor case and see what sticky substance is near the Air Inlet Control Damper.

 

Thanks, that’s exactly what I was looking for.