2021 Ford F-150: EcoBoost stumble and misfire in humid or damp conditions

The 2.7-liter and 3.5-liter EcoBoost engines use a front-mounted air-to-air intercooler. In humid conditions — Gulf Coast summers, foggy mornings, cool damp fall weather — moisture in the intake charge condenses on the cold intercooler core and pools at the bottom. Under light throttle nothing happens. Under a hard pull, airflow picks that water up and delivers it into a cylinder, and the engine stumbles hard enough to set a random misfire code.

Owners describe it as a shudder or a sudden loss of power while merging or passing that clears in a second, sometimes with a check engine light that goes out on its own after a few drive cycles. It is not an ignition failure, and replacing plugs and coils on this symptom is money spent for nothing.

• The clear tell is weather correlation. If it only happens on damp mornings and never on dry days, this is condensation, not a coil.
• Ford has addressed the condition on affected trucks with powertrain software changes and, in some cases, an intercooler drain modification. Ask a dealer to check for outstanding software for your VIN.
• Diagnostic and software update: $0–$200 if under warranty coverage or as a goodwill update.
• A stored P0300 with no cylinder-specific code and no ignition component history strongly favours this explanation over a mechanical fault.