Automakers cut back sharply on production in August after a big gain in July, lowering overall factory output last month.
The Federal Reserve says manufacturing production dropped 0.5 percent, the biggest decline since January 2014. The drop in auto output accounted for most of the decline. Production of computers, airplanes and furniture also fell.
Overall industrial production, which includes mining and utilities, dropped 0.4 percent in August, after a 0.9 percent rise in July.
Auto production plunged 6.4 percent, its steepest fall in more than three years, after an outsized gain of 10.6 percent in July. Those violent swings partly reflect difficulties in seasonally adjusting the data and are likely temporary. Auto sales are strong and on track to top 17 million this year for the first time since 2001.