Engine miss and truck jumps? Hard to down shift? Issue with high gear only?

In most cases the problem you describing is caused by an engine misfire and this type of miss will usually show up under lower RPM such as when the transmission shift into Overdrive and the RPM drops. At more then 100000  miles you should consider replacing all the spark plugs with OE Ford motorcraft spark plugs as well as replacing the spark plug boots. When doing so, be sure to add a small dab of dielectric grease to avoid any spark leakage.

Getting the spark plug out is very major and to do so you need to do it with a totally clean engine. At more then 100,000 miles it would be a good idea to have the injectors professionally cleaned. If you have never changed the spark plugs, you may want to consider having it professionally done as well.

This will help.

Thanks.

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