U.S. safety regulators will investigate problems with stalling or surging engines, in about 725,000 Ford cars and SUVs.
The probe includes affects Ford Escape and Mercury Mariner SUVs from the 2009 through 2011 model years.
The National Highway Traffic Safety Administration and Ford have received almost 1,500 complaints about the problem.
Meanwhile, regulators are considering whether to investigate a complaint from an auto lab in Virginia, that the steering can fail on the Toyota Prius.
A probe would affect the Prius gas-electric hybrids from the 2004 through 2009 model years.