DETROIT — Unemployment is still high and the so-called fiscal cliff is looming, but those worries didn’t slow down the nation’s car and truck buyers in September.

Autos flew off the lot at the highest sales rate in four years, adjusted for seasonal variations, according to the research firm Autodata.

Over all, a total of 1.19 million cars, trucks and S.U.V.’s were sold in the United States during the month — a 13 percent increase from a year ago.

Japanese and German manufacturers led the sales boom, offsetting weaker results at General Motors and Ford.