Towing cylinder 4 misfire

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cullinan18

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When towing 45+ mph on state highways and trying to maintain speed going uphill, I get a shuddering and then Cylinder 4 Misfire error. I thought it was related to my oil catch can, so I switched to the premium brand. Same problem, so I switched back to the OEM pcv hose. The problem still remained on my tow home today. I'll schedule an appointment with the dealer (still have a warranty), but anybody have a thought what could be the cause or how to avoid it (without telling me to stop towing or go even slower)?

I'm at 78,000 miles approx.
 

JasonH

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Pull the code. Probably spark plugs. I had the same issue while accelerating with the camper hooked up...around 90k I think. Supposedly the Ecoboost is hard on plugs and they're done well before 100k miles. I have a thread on here about my experience changing them.
 

JasonH

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Had a misfire last week during heavy throttle. Easily replicated it during full throttle acceleration. It's been around 30K miles since I put new plugs in. I ordered coils for cylinder 2 and 3. Then regapped the plugs down to .028 to .03. Misfire is gone during full throttle. Sending coils back.
 
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