WESTLAKE VILLAGE, Calif. – After changes to emissions technology caused a spike in engine-related problems in recent years, more fleets are reporting improvements in the quality of their heavy-duty engines.

According to J.D. Power and Associates’ 2011 Heavy-Duty Truck Engine and Transmission Study, 42 percent of owners of one-year-old heavy-duty trucks report experiencing some type of engine-related problem, down from 46 percent last year.

However, the survey notes that this is still well above the historically low average of 26 percent in 2004.

The study measures satisfaction among primary maintainers with engines and transmissions one year-old models. Satisfaction is measured based on eight key factors: engine reliability and dependability; engine warranty; acceleration when fully loaded; electronic control module; accessibility to components for service or maintenance; vibration at idle; maintaining speeds on grades; and average fuel economy.

The most-commonly reported engine problems are issues with the exhaust gas recirculation (EGR) valve, said 23 percent of owners, and electronic control module calibration (21%).

Reported engine problems in 2011 fell to an average of 66 problems per 100 vehicles from 72 PP100 in 2010. As a result, satisfaction with engines has increased by 22 points to an average of 739, on a 1,000-point scale.

"It’s encouraging to see that the number and frequency of problems is improving," said Brent Gruber, senior manager of the commercial vehicle practice at J.D. Power and Associates. "With the new technology required to meet emissions standards, today’s engines simply are more problematic than the previous generation."

Navistar’s International MaxxForce engines ranked highest in customer satisfaction with a score of 760 and performed particularly well in four of eight factors in the survey: engine reliability and dependability, engine warranty, vibration at idle and average fuel economy.

Gruber notes, though, that the most recent emissions standards revision took place in 2010.

How those changes will affect quality and customer satisfaction will be reflected in the 2012 J.D. Power study.

"Given the quality issues that arose from new emissions requirements in 2004 and 2007, the 2010 emissions standards will likely create another round of challenges for engine manufacturers," said Gruber. "The manufacturers that best handle the integration of these new standards will have a distinct competitive advantage."

Upcoming fuel efficiency standards recently announced by the U.S. government will put additional pressure on engine manufacturers for the next several years, Gruber added.

"Although engine manufacturers are facing yet another mandate, we expect that the change in improved fuel efficiency will result in higher satisfaction and loyalty for the engine brands."

About 58 percent of owners said they "definitely will" or "probably will" specify the same engine brand in their next heavy-duty truck.