The US government is investigating whether Hyundai and Kia recalled vehicles fast enough.
Officials say they're looking into three recalls by the automakers.
You may recall, Hyundai recalled about 470,000 vehicles in September 2015.
That's because the engines can stall, increasing the risk of a crash.
Last March, Hyundai and Kia issued two more recalls covering 1.2 million additional vehicles due to the same engine problem.
Both Hyundai and Kia say they're cooperating with the investigation.