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So I have had a flashing engine light when I pin it and rev the motor around 4800 (so i slow down) thats happened since I bought my expedition a year ago. I have only reved the motor like that a few times but now the motor runs extremely rough when the truck has been rained on all night it started about 3 months ago but when she warms up by sitting after a hot motor is turned off it's fine and the check engine light turns off now every time this has happened I'm going to work so I can't get to my mechanics until after work or the weekend and the code has disappeared with no back up So finally I got my code read and it said misfire on cylinder # 5. So I checked all the wiring taped up the connection from wire to conector Then started the truck. The truck still runs like **** I'm so pissed. For f. Sake. How can a coil be this spastic in causing misfires and how the he'll can moisture find a way in. Please help. Thank you.
Replace the #5 COP, that the problem. Down inside the spark plug well the rubber boot material is breaking down and allowing spark to jump to the sidewalls instead of getting to the spark plug. You can try just changing the rubber boot first. The boot is about $3 at an auto parts store and a new coil off eBay (with the boot) is about $8.