There may be an oil residue on the disc in the accelerator work unit, and therefore, the frictional force between the disc and the plate my gradually increase. If this problem is left unattended, the accelerator position sensor may become slow to return to the idle position, and in the worst case, taking the foot off the accelerator pedal would not bring down the engine revs to an idle. Incidentally, even if this worst case should happen, the driver can stop the vehicle with brake operation, because the vehicles subject to this recall are equipped with brake override system, which will reduce the throttle opening.