What's the sensor underneath the engine air filter - 2003 24vVR6

[HeyCrutch]

Having a TON of fun getting this "parts" van running and cleaned up. It's crazy how much satisfaction I'm getting with working on this $1000 van (has 175k on it). Everything feels like a "win" and I'm not all that worried about making a mistake when working on it. Perfect van to learn on. With the other two "more expensive" lower mileage vans, I tend to think the sky is falling with every novel noise.

Aaaaaanyways ... on to the parts van (a 2003 GLS).

While preparing to install a new engine air filter, I noticed oil in the flexible connecting pipe/hose on the Air Intake, right around where the tension clamp is that holds it onto the air filter box. There was a fair amount of sludge around the area beneath the connection between the Air Filter Box and the main intake assembly (and on top of the washer fluid reserves) so there's obviously been a fair amount of oil that has leaked out from this connection point. I've read on another forum that it could be vacuum, it could be overfilling oil, and it could be PCV valve related.

I cleaned it up the hose connections and inspected the MAF sensor -- it looks to be clean but I might spray some MAF sensor cleaner on it next time. I put a new engine air filter in and as I was doing so, for the first time I actually looked around under the filter and saw a sensor that is in there as well as two different intake pipes for inbound air (one towards the exterior of the van above the wheel, and one towards in interior of the engine bay (not connected to anything though). No idea if the door that looks to close off either side is mechanically controlled (or maybe it moves on its own based on air flow or air temp?)

So, what's happening down there, in terms of the sensor and the two different intakes, and the flap/door in terms of air flow for the engine? . All of this is UNDER the filter itself in the filter box.

^ This is the question I'm seeking an answer on, as a start. All the rest is ancillary.



CEL Side Note - the van throws P1151 - bank 1 mixture adaptation range 1, so I think that I might have a vacuum leak (or a clog, given the oil I discovered) on one of the hoses that is part of the air intake system. It's also possible the PCV portion of the air intake has failed. From the drivers seat the engine seems to run great - as well as either of the other two I own. (The main issue with this van is the trans).

I've NEVER checked vacuum, so that's a skill I'm about to learn.
_________________
-2003 EV MV Wk - Forest - 51k
-2002 EV Camper - Ghost - 82k
-2003 EV GLS - Fluffhead - 176k

-1997 EVC - 12vVR6 (SOLD 5/2025)

[trunnion]

That's not a sensor. It's a wax motor that closes the flap leading into the engine bay when the temperature inside the airbox is high enough to melt the wax. When the temperature is hot, the flap closes to draw air only from the fender intake. When the temperature is cold, the flap allows warm air from the engine bay to mix with the cold air from the fender intake.

This feature, along with the coolant channels in the throttle body, is designed to prevent the throttle from icing up during cold weather operation.

[HeyCrutch]