1991 Ford Explorer performance

Does your explorer have a tach?

yes it does

Ok good you will need to drive the vehicle and get it up to about 45 or so make sure you felt is shift into all 4 gears and into lock up. Now with you left foot while maintaining speed press on the brake pedal just enough to turn on the brake lights and release did the rpm change about 200 rpm or so? This will tell us if the trans is one shifting right and if the lock up solinoid is doing its job helping to for now rule out trans. I need to know if you have a digital mutli meter to test a couple of things?

I did what u said and the rpms go up about 200-300 rpms. I pulled in the driveway and reved it up to 1500rpms (in park) and it misses alot. So I waited till dark and put it in my poll barn where its completley dark and started it. U can see the plug wires arching to metal in places, I just replaced the wires about 20 thousand miles ago, thats why I didn't think of the wires at first. Do they go bad that fast? I won't have time to change them till Wendsday. I don't drive this car very often, its my sons car. I can get a meter if I need it.

well change the wires first you got some bad ones or really cheap ones, either way have them warranty them and then see how it runs. As for a meter just make sure to get a digital multi meter don't need to cost alot a 20 dollar one will work just fine. Let me know how it goes.