general problems of the 2010 Mercury Mountaineer

While driving the Mountaineer I was slowing for a stoplight shortly after starting it up (had driven about 1/3 mile). The engine suddenly started to speed up and required significant extra braking force to come to a stop. I put the car in nuetral and the engine ran at about 3,300 rpm for about 10 seconds. This is the third time this has happened. The first time the thermostat was replaced. The second time the throttle body was replaced. The third time the vehicle was checked but no defect could be found. The second time I also put it in nuetral and it also ran at about 3,300 rpm for about 10 seconds.

Pulled into parking space, placed shifter in park, turned off ignition, released brake and vehicle rolled backwards as if not in park. Attempted to restart vehicle and no response. Set parking brake. Could not get vehicle to lock into park, shifter moved regardless of brake on or not and would not start. Moved shifter through entire range of gears and returned to park, vehicle still would not start and park would not hold. Called dealer and was told to have it towed in. Returned to vehicle and tried once more and it started and proceeded to respond normally. Vehicle taken directly to dealer who could not find any problem or cause of preceding situation. On two subsequent dates (most recent 5/25/2012), vehicle was backed into a parking space, placed in park and ignition turned off. When an attempt to restart vehicle was made there was no response. Park appeared to hold normal, but unable to engage ignition. Dash lights, chimes and all electrical components appear to work normal but was still unable to engage starter. Again started process to have vehicle towed to dealer. After approximately 30 minutes to an hour of sitting (with no other action) vehicle started normally. Again dealer at a loss for cause and cannot effect repair since unable to recreate problem. Concern is for transmission/ignition interlock failure or other action that could result in damage or injury.