98 explorer missing uphills

Have a 98 explorer with a 4.0 X engine. Had the #3 injector go out and replaced. Idles fine now but when try to accelerate up a hill it has no power. Does anyone have an idea waht could be wrong. Thanks!!!

Check the spark plug wires for a good fit on the plugs. One might not be on far enough which would cause it to miss up a hill. IF you have never replaced them now is a good time.

Thanks Dave, I should have said that I already replaced the plugs and plug wires before I figured out that the injector was bad. Getting my scanner back this weekend to figure out what new code is there now.