UPDATED: 4//11/14 12:34 pm ET - adds other closed cases
DETROIT (Reuters) -- U.S. safety regulators said today they have closed an investigation into complaints of reduced power in Ford F-150 pickup trucks, stopping short of requesting a recall.
Ford came up with a protective shield that kept condensation from developing to the point of causing the engine to misfire . Dealers were informed through a series of technical service bulletins, and NHTSA was satisfied that the problem was solved without Ford conducting a recall.
Last May, the National Highway Traffic Safety Administration opened an investigation into F-150 pickups from model years 2011 to 2013, which accounted for about 360,000 vehicles made by Ford Motor Co. Each of the pickup trucks has a 3.5-liter EcoBoost engine.
In its report, NHTSA said: “When the driver requests more power from the engine, as in accelerating to pass, merge, ascend hills or haul a load the two turbochargers will spin up, compressing the air which is then used to increase the power created by the combustion in the engine. The compressed air, which gains heat by the compression process, is passed through a charge air cooler, which is designed to lower the temperature of the air in order to make the combustion process even more efficient."
NHTSA received 525 complaints and Ford informed NHTSA of 3,731 more that the company received. Nearly 19,000 warranty claims may have been involved. No injuries, or crashes were reported to Ford or NHTSA.
During the investigation, Ford told NHTSA that a misfire could occur in its 3.5-liter EcoBoost engines which have twin turbochargers under significantly humid and rainy conditions because condensation could form, leading to the misfire of up to three cylinders.
As it does when it closes an investigation, NHTSA reserved the right to seek a recall of the affected vehicles in the future.
Hyundai, Nissan cases
Meanwhile, new records made available by NHTSA today show the agency closed two other investigations in recent weeks: one of the 2009-12 Hyundai Genesis, and one of the 2013 Nissan Pathfinder and Infiniti JX.
Hyundai recalled 43,500 units of the Genesis in October to replace brake fluid that did not sufficiently prevent corrosion inside the hydraulic electronic control unit, and could make the brakes less effective. The main fix was to flush and replace the brake fluid. For cars made before June 1, 2010, Hyundai said it would have dealers inspect the control unit and if corrosion had occurred, replace it.
NHTSA opened an investigation to see whether the 45,639 cars made after June 1, 2010 needed the same treatment, or whether replacing the brake fluid would be enough to prevent damage. Investigators found that the newer cars had a warranty claim rate of 0.1 percent, compared to 7 percent for the older cars, suggesting that the faulty brake fluid had not yet caused a significant number of problems.
The agency closed its investigation April 4.
The investigation into the Pathfinder and JX began last year, after NHTSA received complaints of noise and vibration leading to transmission failure in Pathfinder vehicles. Last month Nissan recalled 3,065 Pathfinder vehicles built between April 18, 2012 and October 3, 2012, saying that insufficient hose clamping force could cause the internal transmission oil cooler (ITOC) hose to detach from the cooler.
NHTSA kept open its investigation to compare these 3,065 vehicles to the remaining 120,474 Pathfinder and JX vehicles from the same model year. Investigators found that the newer cars had a warranty claim rate of 0.1 and 0.2 percent, compared to 8.5 percent for the older ones, suggesting that Nissan had isolated the problematic vehicles.
That investigation closed on March 31.
Gabe Nelson of Automotive News contributed to this report.