DETROIT (AP) — A U.S. safety agency has ended an investigation into complaints of unintended acceleration in three Ford vehicles.

The probe covered about 169,000 Ford Five Hundred and Mercury Montego sedans, and Ford Freestyle wagons from the 2005 through 2007 model years. It was started in May of 2011 after the National Highway Traffic Safety Administration received complaints that the cars can lunge when driven at low speeds.

The agency says Ford traced the problem to deposits in the throttle body. It extended warranty coverage for the problem to 10 years or 150,000 miles. Ford will clean the throttle and reprogram computer controls.

The agency says the fixes take care of the problem, which was controlled easily by moderate braking.

The investigation found about 4,000 complaints and one crash causing an injury.