I have a metal valve stem cover (screws on) that will not come off. When I try turning it the stem turns also. I tried grabbing the stem with one wrench & grabbing the stem cover with another wtench but I just stripped the hex grooves off the cover. I've tried everything I can think of, any ideas? Has anyone else had this problem?

might have to pull the tire and change the stem

Since you've ruined it anyway, get two pair locking pliars and go to town.

First the cruise buttons, now this? Do you work at a syrup factory?;-)

I was going to use 2 pairs of vise grip pliers but I didn't want to smash the end of the stem.
Last summer, while the E was parked for a week at airport extended parking I left an unopened can of Coke in the car. When I got in the car it had exploded all over everything! I've cleaned the entire interior many times to get that sticky mess out, but I think it got into the cruise buttons. By the way, don't ever let that happen, its the worst mess I've ever seen!

go to home depot and get some pb blaster that stuff loosens pretty much any bolt or screw that is stuck.

If you have a Dremel Motor tool or the like you can use a metal cut-off wheel to cut the cap off.

Dremel tools can be a real labor saving device. I've used mine to cut the clips off a parking brake cable, rusted headlight bezel rings, and a ton of other things I can't remember.

Take your time with the 2 pairs of pliers. You may cause the stem to start leaking. I would just go to a tire place have them cut the stem off, then put a new one in. That's far less trouble, than what you have gone through already.

Dom

Unless you have removed them 2007+ have TPMS sensors. You may want to take it to the dealer or tire shop before you accidently snap off the valve stem part of the sensor and leave yourself with a flat tire.

Dremel tools can be a real labor saving device. I've used mine to cut the clips off a parking brake cable, rusted headlight bezel rings, and a ton of other things I can't remember.

You've got that right! I regularly try them on harder/tougher problems than I really should for the constructed capacity of these Dremels and, with patience, have found them a lifesaver. Have two now and lots of attachments. I originally bought one as a replacement for an underpowered chain saw sharpener, thinking a non-dedicated unit would be more useful. Sure was right.:-)

Spray on some WD40!

When using metal valve stem caps on stems with TPMS sensors a galvanic effect takes place and can corrode the cap and stem together. Be sure to use plastic caps or TPMS approved caps.

Here's a section from a manual I found online-

It is also important to use the plastic replacement cap to ensure that a dissimilar metal
cap is not used to contact the aluminum stem. Field studies have shown that using a
dissimilar metal cap (brass) can cause galvanic corrosion between the cap and the
stem, resulting in the cap being stuck to the stem. Use of excessive force, or
improper tools, can also damage the cap and or stem.