I have a 94 Cherokee and have one tire that has been consistently running low on air the last couple of months (20 psi vs. standard of 33 psi). I took it to NTB and they said they couldn’t find any sort of leak in the tire. Is there another reason why only one tire would be running low? Thanks in advance for any help!

 

It's either got something poking through the tread you didn't see, the valve stem is leaking, or the bead is leaking. Mix up some soapy water in a spray bottle and start spraying the tread area. Look for bubbles.

 

Which is what NTB should have done. Moderate amount of dish soap in a bucket of water. I prefer a rag to slop the soapy water on instead of a spray bottle which tends to make foam. As IJM mentioned, look around the beam where the rubber meets the rim, around the valve stem, take the cap off and soap the end in case the valve is leaking internally. You've got a slow leak, so be patient looking for the bubbles. When you find it, mark it so the guys at NTB can find it.