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Actually the 5.4 is a great engine and about the the only problem the 5.4 had was spark plugs blowing out and the timing chain phasers. Both have been dealt with but they still have a problem with spark plugs not wanting to come out.
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In most cases you will be fine, but the trick is to not let the spark plugs stay in the engine the 100k Miles that Ford recomends. Change them out at 60K.