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

Question

My 2013 F-150 has developed a nasty shudder when I try to pass someone on the highway. If I'm cruising at 60 and step on it, the truck starts bucking and the Check Engine light flashes at me. It usually goes away if I let off the gas.

Scanner shows a P0306 for Cylinder 6 misfire. I replaced all the spark plugs about 10k miles ago with iridiums. Is this the dreaded CAC condensation issue I've read about, or just a bad coil pack? It seems worse when it's raining or humid outside.

ReganRegen · Accepted Answer

✅ Confirmed fix: On the early EcoBoosts, the P0306 under boost is almost always the ignition coil failing or the spark plug gap blowing out. However, the root cause is often moisture in the Intercooler (CAC).

I replaced the Cylinder 6 coil pack and drilled a 1/16" weep hole in the lowest point of the intercooler to drain the accumulated gunk/water. The truck hasn't stumbled since, even in heavy rain. Also, make sure you are using Motorcraft SP-580 plugs gapped strictly to .030".

ReganRegen · Answer

It's classic carbon buildup on the intake valves. Being a GDI engine, the 3.5 EcoBoost doesnt have fuel washing the valves. You need to pull the manifold and walnut blast the valves to get the airflow back to normal, otherwise, you'll keep getting those high-load misfires.

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

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