DETROIT ? For the first time in five years, the average quality of new cars and trucks failed to improve this year, while domestic automakers continued to gain ground against foreign brands, according to a closely watched study of 2003 models.

Toyota Motor Sales USA Inc. repeated as the automaker with the highest overall initial quality, recording an average of 115 problems per 100 vehicles, eight more than last year, according to the annual report released Tuesday from J.D. Power and Associates.

Toyota’s Lexus brand was tops among all nameplates with 76 problems per 100 vehicles — 27 fewer than No. 2 Cadillac.

Among manufacturers, Toyota was followed by Porsche Cars North America Inc. (117), BMW of North America (124) and American Honda Motor Co. (126).

Those were the only automakers to score better than the industry average of 133 problems per 100 vehicles. That matched last year’s performance. The industry as a whole showed steady improvement between 1998 and 2002, posting an average annual quality improvement of 6.7 percent.