1997 Ford F150 Starter

Welcome to the site. How long since a tune-up? If you have a digital multimeter, I'd take an inductive reading from the plug wires, engine idling. It's not a conclusive test, but as a first quick test, and you don't take anything loose, you don't penetrate the plug wire insulation and don't take the plug wire loose. Even one of the low end dmms will give an inductive reading, you just touch the dmm lead to the plug wire, ground the other lead. Say, most the readings show about 1/2 volt and one or two others show zero. I know where to start checking. There are other things that might cause that, like a vacuum leak or egr, something.