My '05 F150 has a rough idle and when going up hills, loses power an the engine light flashes and it struggles to go over 40mph.
The check engine light is flashing to warn you that the engine is misfiring and damaging the catalytic converter. I'd suggest doing a tune up first. HTH. -Jim
Change the plug wires along with the plugs. A tune-up should include changing the wires also.
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