Ford 3.5 EcoBoost

Ford's twin-turbocharged 3.5-litre V6 — the engine that made a boosted six a credible replacement for a V8 in the F-150, and which also powers the Explorer, Expedition, Transit and the Raptor.

The first-generation engine's characteristic complaint is condensation in the charge-air cooler: in cold, humid conditions water collects in the intercooler and is drawn into the engine in slugs, producing a violent misfire and stumble under acceleration in exactly those conditions. It is a real and well-documented behaviour rather than a component failure, and Ford addressed it through calibration and hardware changes — a misfire that only happens in cold damp weather on one of these is this until proven otherwise.

The timing chain and its cam phasers are the second theme at mileage, announcing themselves as a start-up rattle. Second-generation engines added port injection alongside direct, which largely resolved the intake-valve carbon the first generation accumulated.