Key problems

My 1990 Cherokee's been having some issues with the door key on the driver's door lately, recently it's been getting harder and harder to turn the key and last night and today the key didn't work in the driver's door, almost as if it was the wrong key but this evening I tried the key again and it's perfect, better than it's been in weeks. So what could be my problem?

The key is worn. Keys are made of brass, the disc tumbers are spring steel - they'll eventually wear the keys down.

That's why you keep one good, sharp copy of each key that you don't use - it's the "master" for when you need new keys.

You might be able to make a new key from yours, but no guarantee they'll work. It's a little better than half, tho...

5-90

Pull the drivers side door lock cyclinder out(if its the same as your ignition) and take it to a locksmith. There is a code on it and he can cut a new "master" key from it.

This is a common problem with Jeep and Chrysler door locks. The wafers are made out of brass and wear out. The body of the lock is made out of die cast and can wear uneven causing the wafers to stick. If your key works fine in the ignition and other doors then making a new key may not fix your problem. Remove the lock and take it to a locksmith. For about $15.00-$25.00 or so, you can have it fixed and/or replaced.
Btw, there is no code on the driverside lock!

Forgot to add that my only problem was the driver's side door lock and the 'master' I made awhile ago didn't work either, I've got a different key for the ignition.

I don't know if they still used GM style locks & keys in 1990 but they aren't very good. My driver door locks always eventually wear out. My problem usually starts out with the little brushed metal key slot coming undone then it's tough to get the key started (especially in the dark) without a lot of farting around. Squirt in some of that nasty black graphite lock-eze and it'll probably help slide the key in easier. But I know someday it's going to fall completely apart or the key is going to break off inside, because they always do.

You can get a new lock cylinder re-keyed at a good lock shop to match your other doors & glovebox.