This was a learning experience for me, and I hope never happens to you. I got some cheap black metal valve caps for my tires, just to see if they looked good. Well, after a few months I had my tires rotated, and the techs must have tightened them down more than I have. I went to check the pressure, and none of them would twist loose. I went back to the store and the manager and I spend 15 minutes wrestling the caps with a wrench, pliers, anything thy had to get them off. I finally got four of the five off, but the one on the spare was not moving!
That was a week ago. Today I wanted to give it another shot, so I went to O'Reilly auto parts to see if they had anything better to get into the small area where the stem is. I couldn't hold the stem tight enough, it kept spinning in the wheel. Then I went to the Jeep dealership, and I walked back with one of the techs and picked out these narrow jaw locking pliers. That's what I needed to get a good grip on the stem, and be able to put smaller locking pliers on the cap. After about five minutes of him and I wrenching on it, I finally got the interior pliers locked on the stem tight enough that I was able to spin the damn cap. @!!!!!#YFJBA
It was a relief finally getting it off, because I have beadlock wheels, and it would have been a lot of time or money to get the tire off, just to replace the stem.