2013 Ford F-150 P0306 Misfire under load - EcoBoost shuddering

Question

My 2013 EcoBoost has developed a nasty shudder when I'm trying to pass someone on the highway. If I step on it, the whole truck shakes and the Check Engine light flashes at me. Once I lift off, it goes back to steady on. Scanned it and it's always P0306.

I changed all the plugs about 15k miles ago, so they shouldn't be bad already. It only happens when it's humid or raining outside, which is weird. It feels like a dead miss, but only when the turbos are actually building boost.

ShopBossMike · Accepted Answer

✅ Confirmed fix: Found a cracked ceramic insulator on the spark plug for cylinder 6. Even though they were relatively new, the high boost levels on these engines are sensitive to gap growth and carbon tracking. Installed a fresh set of Motorcraft SP-580 plugs gapped strictly to 0.030 and the shudder is completely gone under all load conditions. Also made sure to use dielectric grease on the boots.

FleetMech_Ed · Answer

The early 3.5 EcoBoost engines are notorious for moisture buildup in the Intercooler (CAC). Under high humidity, condensation pools in the bottom. When you go wide open throttle, that water gets sucked into the intake and blows out the spark. You need to look into the 'drill a tiny hole' trick or check for a TSB regarding the CAC air deflector.

2013 Ford F-150 P0306 Misfire under load - EcoBoost shuddering

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