Lyons said some accelerator assemblies could be replaced in their entirety and in other cases existing accelerators could be repaired.
He said Toyota engineers determined that the accumulation of water in an interior part of the pedal assembly was causing excessive wear, "making the pedal slow to return to idle."
The company said owners should continue to drive their cars but be aware of a possible problem with the gas pedal.
"It happens only rarely," said John Hanson.
Safety experts say Toyota owners should practice shifting gears to neutral in case their cars experience a runaway condition.
ABC News' Drew Sandholm contributed to this report.