Small vacuum hose on back Airbox 4.0

Have a broken vacuum fitting on the back of air box wondering if any anyone knows what purpose this serves ? Truck seems to be running ok no check engine lights
2012 4.0

 

It goes to the fuel pressure regulator. It's there to serve as a atmospheric pressure reference for the regulator.

If you leave the broken nipple and do not seal the leak, you're letting un-metered air enter the intake tract. That'll cause you to run lean. You might not get a CEL out of it, but your fuel trims will suffer. In addition to that, your fuel pressure regulator's internal diaphragm is now open to the atmosphere (and therefor dirt) which can cause issues over time.

Ideally, you'd want to seal that broken nipple, and plumb a new hose barb into the airbox so your not letting unmetered air into the system, and your FPR is referencing filtered air.

 

Ok thanks ..was trying to find a replacement for it but not sure what that housing is called ?

 

Get one at a junkyard

 

Good idea thanks

 

This happened to me today (nipple broke off during throttle body cleaning). Was able to use a toothpick to line up the nipple with the airbox hole, then use JB Plastic Weld and Gorilla Glue on the broken seam and outside of the nipple for a hopefully long-term fix. The toothpick also helps to make sure the hole remains unobstructed from glue. It's curing overnight for now but so far it seems pretty rigid.

The camera flash makes it look a lot worse than it is.

 

You can use a plastic barbed fitting and drill and tap it for 1/8” NPT. That’s what I did to replace mine and not buy another air box

https://www.usplastic.com/catalog/item.aspx?itemid=35510&clickid=ltk-email&trk_msg=8IUSC18OD90KPBT8CSAJOIQSJG&trk_contact=MD7GJSGCQJPH0VI8EV77L67V7C&trk_module=tra&trk_sid=RS7SHF3MG1R8RUACH7VRDBM564&trk_link=E2B0O1EV4L44V80JK897P31UVC″_Tube_ID_x_1/8=″_NPT_Black_Nylon_Threaded_Adapter=

 

Agreed, this will probably be the route I go as well after the holiday road trips. Especially because the hose is rather short and puts slight downward pressure on the fitting, so I don't expect my slathering of JB Plastic Weld will hold up long term.

As a slight update, my original temp fix broke with a "wiggle test" so I added even MORE JB Plastic Weld all around it, and then once the hose was connected and a zip tie to keep it on, even MORE JB slathered all around haha. About as hack a job as you can get...