Porsche Cars North America rockets to the top of the influential J.D. Power quality rankings, a sharp U-turn from 2005, when the sports car brand finished 32nd out of 36 auto makers.

On the strength of the Porsche Cayman sports coupe, launched last year as an ’06, the auto maker averaged 91 problems per 100 vehicles in J.D. Power’s Initial Quality Study (IQS) – a 38% improvement compared with last year’s 147 problems per 100 vehicles.

The lower total also was well below the industry average of 124. But this year’s average suggests quality erosion because it reverses two years of improvement.

Last year, the industry average was 118 problems per 100 vehicles, one notch better than the year before.

The increase may be attributed to a more detailed survey format that potentially could discover more problems than the previous research. But J.D. Power also notes vehicles might be more problem-prone because they are increasingly complex.

“New vehicles today are often packed with new technologies that unfortunately can be complicated and frustrating for the average consumer when their integration is not well executed,” says Joe Ivers, J.D. Power’s executive director-quality and customer satisfaction research.

“In the eyes of consumers, design flaws can have as much of an impact on their perceptions of quality as can a defect. Yet, many manufacturers have tended to addres quality solely on the plant floor without considering design factors.”

The study is based on survey responses from 63,607 purchasers and lessess of ’06-model vehicles and tracks their first 90 days of ownership.

Toyota Motor Corp. and its Lexus brand – which finishes second to Porsche with an average of 93 problems per 100 vehicles – dominate vehicle rankings by taking the top spot in 11 of 19 segments.

Porsche and Lexus lead the luxury segments, with the Cayman claiming the title for highest-quality vehicle, overall.

The Cayman shares a significant number of components with the proven Porsche Boxster.

Porsche and Lexus also are atop the overall standings, followed by Hyundai Motor Co. Ltd.’s score of 102. Hyundai continues its climb that began in earnest two years ago when the Seoul-based auto maker beat the industry average for the first time.

Toyota’s namesake brand takes five segment awards to lead the non-luxury products.

Brands making significant jumps include Nissan, Chrysler and Chevrolet. They outperform the industry average this year, after scoring below that benchmark in 2005.

Volkswagen, Isuzu and Land Rover finish at the bottom. Land Rover is dead-last with 204 problems per 100 vehicles, compared with 149 in 2005.

Toyota’s plant in Iwate, Japan, takes J.D. Power’s platinum award as the top plant. Iwate builds the Lexus ES 330.

General Motors Corp.’s car plant in Oshawa, Ont., Canada, is the top North American plant for the second consecutive year, while the Graz, Austria, site run by Magna Steyr Fahrzeugtechnik AG & Co KG, is named top European plant.

emayne@wardsauto.com