WESTLAKE VILLAGE, Calif. — The initial quality of 2011 new model launches has declined considerably compared with improvements from 2007 to 2010, according to the J.D. Power and Associates 2011 U.S. Initial Quality Study (IQS). The study reviews new-vehicle quality measured at 90 days of ownership.

Overall initial quality improved to an average of 107 problems per 100 vehicles (PP100) in 2011 from 109 PP100 in 2010, while the initial quality of launch models — those that are all-new or have had major redesigns — worsened by 10 percent to an average of 122 PP100 in 2011.

Carryover models, however, have better initial quality than ever before, the study showed. Owners of these vehicles reported an average of just 103 PP100 in 2011, compared with 108 PP100 in 2010.

“Exciting models with the latest features are crucial for winning over today’s demanding consumers,” said David Sargent, vice president of global vehicle research at J.D. Power and Associates. “However, automakers must not lose their focus on the importance of these models also achieving exceptional quality levels. Expected reliability continues to be the single-most-important reason why new-vehicle buyers choose one model over another, and no manufacturer can afford to give consumers any doubts regarding the quality of their latest products.”

Compared with 17 models in 2010, only seven all-new or redesigned models ranked among the top three of their respective award segments. Only one launch model received a segment award for 2011, compared with five launch models in 2010. One-fourth of redesigned models performed better than the outgoing previous-generation model did in 2010, and eight all-new models performed above their respective award segment average.

The decline in vehicle launch quality is evident most notably in the engine/transmission and audio/entertainment/navigation categories. The two primary causes for the quality decline were redesigned engines or transmissions that led to hesitations when accelerating or changing gears, and multimedia technology that was not intuitive or did not function properly on a regular basis.

“Clearly, consumers are interested in having new technology in their vehicles, but automakers must ensure that the technology is ready for prime time,” Sargent said.

Overall problem rates for audio/entertainment/navigation systems in 2011 were 18 percent higher than in 2010 and 28 percent higher than in 2009.

Lexus led the overall nameplate rankings with 73 PP100 on average, followed by Honda, Acura, Mercedes-Benz and Mazda. Land Rover posted the largest improvement in 2011, reducing problems by 47 PP100 from 2010.

Honda captured seven segment awards for the Accord, Accord Crosstour, Civic (in a tie), Element, Fit, Insight (in a tie) and Ridgeline. Lexus received four segment awards for its ES, GS, GX and LS models. For a second consecutive year, the Lexus LS had the fewest quality problems in the industry with 54 PP100.

Chevrolet received awards for the HHR and the Tahoe, Ford for the F-150 and the Taurus, and Mercedes-Benz for the GLK-Class and the E-Class cabriolet/coupe. The Cadillac Escalade, Chrysler Town & Country, Dodge Challenger and Mazda MX-5 Miata received segment awards as well.

Among all-new and redesigned models, the Hyundai Equus and Dodge Durango each ranked second in their respective segments.

Three assembly plants received Platinum Plant Quality Awards for producing models yielding the fewest defects and malfunctions: the Toyota Motor Corporation Cambridge South, Ontario, Canada, plant (which produces the Lexus RX); the Toyota Motor Corporation Kyushu 2, Japan, plant (which produces the Lexus ES, IS and RX); and the Honda Motor Company plant in Greensburg, Ind.

In Europe and Africa, Daimler’s Bremen 1, Germany, and East London, South Africa, plants tied for the Gold Plant Quality Award.

The 2011 U.S. Initial Quality Study is based on responses from more than 73,000 purchasers and lessees of new 2011 model-year cars, trucks and multi-activity vehicles. The study is based on a 228-question battery and was fielded between February and May 2011.