The investigation, opened Wednesday, covers an estimated 360,000 of the sedans. The probe could lead to a recall, but so far none has been ordered by National Highway Traffic Safety Administration, a federal safety agency. The investigation does not include a nearly identical car, the Mercury Sable.
NHTSA said on its website that 14 people have complained about the problem. No crashes or injuries have been reported. Drivers have reported that it was hard to stop the car with brakes. Several said they had to shut off the engine or shift into neutral to stop. One driver ran a red light and entered an intersection before the car could be stopped.
The agency says the cruise control cable may become detached and hold the throttle open.
Ford spokesman Daniel Pierce said the company is cooperating in the probe. He said the company was just notified of the investigation and he did not know why the Sable was not included.
One driver said in a complaint to NHTSA on Aug. 27, 2010 that a 2006 Taurus began to accelerate without any pressure on the gas pedal. The driver pushed the brakes to the maximum, but the car ran a red light and stopped halfway into an intersection. The engine revved until the driver shut off the car, and it revved again when it was restarted.
"This is an extremely dangerous situation," the driver wrote. "There needs to be something done about this before it becomes fatal."
On Nov. 27, 2011, a different driver reported that the brakes couldn't stop the car, which went through a red light and around two cars, reaching 70 mph before the driver put it in park and turned it off.
"Wow. The scariest thing I have ever experienced," the driver wrote. "If there was heavy traffic someone would have been killed, no doubt in my mind."
NHTSA knows the identity of people filing complaints but does not release their names.
The investigation is likely to be expanded to include the Sable, the Taurus' twin from the defunct Mercury brand. NHTSA said in a statement that investigations generally include cars that use the same parts as cars under investigation.
NHTSA said that it began the investigation to assess the scope, frequency and safety-related consequences of the problem. The agency posted documents outlining the probe on its website over the weekend.
Customers with concerns about their cars can call Ford at 1-866-436-7332.