The issue revolves around the Ford F-150 – specifically those equipped with the 3.5-liter EcoBoost engine – of which some 360,000 were built in the 2011, 2012 and 2013 model years. After receiving an initial 95 complaints, NHTSA opened an investigation last May – almost a year ago – into the reported issue of reduced engine power under hard acceleration. The agency has since received a total of 525 such complaints, and Ford itself reported receiving over 4,000.
Together, NHTSA and Ford determined that the problem resulted from cylinders misfiring, an issue itself stemming from water getting into the charge air cooler (CAC) mated to the turbochargers. In particularly humid or rainy conditions, water was found to get into the CAC, causing some of the cylinders to misfire, which in turn triggered the ECU to disable those cylinders in order to protect the catalytic converter from damage.
Ford conducted its own testing and, rather than issue a recall, published a series of technical service bulletins prompting dealers to install deflect shields onto the CAC in the vehicles in question, solving the problem to 95-percent effectiveness in 2011-12 models and 100 percent in 2013 models. Apparently satisfied that Ford had resolved the issue, NHTSA has closed the file on this particular case.