NEW YORK — The National Highway Traffic Safety Administration said Sunday that it was investigating consumer complaints about “sharp reductions” in acceleration on 2011 to 2013 Ford F-150 pickups that are equipped with the 3.5-liter EcoBoost V-6 engine.
The action, called a preliminary evaluation, covers about 400,000 of the F-150 pickups, the safety agency said. A Ford spokesman, Michael Levine, wrote via e-mail that although the number of vehicles affected was probably more than 325,000, the agency’s figure was too high.
The F-150 is one of the automaker’s most popular, lucrative, and thus important vehicles.
And the twin-turbocharged EcoBoost V-6 is one of Ford’s main engines, used to power not only the F-150 but also sport utility vehicles like the Explorer, crossovers such as the Flex, and cars such as the Taurus.
A Ford spokeswoman, Kelli Felker, wrote in an e-mail that the company was aware of the inquiry and will cooperate with the safety agency.
The agency decided to investigate after receiving 95 complaints from F-150 owners saying they had experienced unexpected power loss during hard accelerations. About one-third of those complaints said the problem had occurred in damp or rainy conditions. There were no reports of accidents.
“Attempting to pass a vehicle accelerating from 55 miles per hour and truck either stutters or stalls,” one owner wrote to the agency in February 2012. “This almost caused a head-on collision. I am scared to pull out in traffic or pass anyone.”
The safety agency said Ford had sent three technical service bulletins to dealers telling them how to cope with “intermittent/stumble misfire on acceleration” in humid or damp conditions.
The EcoBoost is a family of engines in various sizes. Ford has widely promoted the EcoBoost’s turbocharging and direct-injection technology as providing excellent power as well as fuel economy.
The investigation covers only the 3.5 liter V-6, which made its debut in the F-150 for the 2011 model year. In 2012, about 43 percent of the F-150s were equipped with the optional 3.5 liter engine, Levine wrote in an e-mail.
If investigators find additional reason for concern during the preliminary evaluation, it would be upgraded to an engineering analysis. A preliminary evaluation does not typically result in a recall. That outcome is more likely — but not certain — with an engineering analysis.