Engine stalls

Will not not stay running over 5500 ft. Unfortunately for me, the kids and grand kids all live in the mountains, east and west coast.

It has a minor "stumble" upon accelleration at any elevation, hot or cold, and at any speed. Going downhill, the "stumble" might be a bit worse.

It begins to surge in long slow surges, the engine becomes indiferent to throttle position, and then it dies. 10 or 20 min. Later, it will start, but the throttle is completely unresponsive. Attempts to drive it result in the slow surges of power again until it dies. Going down hill after this happens doesn't change the engine performance.

After one of these spells, the transmisson, for the next hour or so, when going down a grade, begins choosing any gear it wants to, with no change to shift knob. Cruse control holds the vehicle speed, the the engine sounds like it's going to explode.

By the time I get it to the dealer, there are no codes for him to find, he says. He says I'll have to "leave it shut off and have it towed to a Toyota dealer immediately to get the codes" is the only solution.