According to the National Highway Traffic Safety Administration, over 50 drivers have complained about the problem affecting 2000 through 2003 older-model Ford Taurus and Mercury Sable cars. Drivers say the throttles stick, causing uncontrolled acceleration.
No recall has been issued yet, and Ford says it's cooperating with the investigation.
"Until we are able to gather more information and complete our own investigation, we cannot speculate as to what actually occurred during the reported incidents," Ford spokeswoman Marcey Zwiebel said.
More than 300,000 vehicles could be affected.
No crashes or injuries have been linked to the problem, according to NHTSA.
The Associated Press contributed to this report.