I work at lot with Ford expedition diagnosis on another forum. Same basic engines. We have had a few members that had a problem with a faulty valve lifter on their 4.6/5.4 engines. Their were two that I remember that had a valve rocker arm fail. If you hear your noise coming from intake/ head area and not front of cam chain area. Your probably looking at a cylinder head issue. If you want to check your Exaust manifold, get in their and snug the bolts up carefully. If they seem rusty or stuck, stop. After put on a thick garden or mechanic glove, fire up when cold to lightly warm, run your hand along manifold feel for leaks. Do the same at collector where header goes to donut. 90 percent of tests on your vehicle can be done at home.
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