2001 Ford Focus SE stalls when warm

Our Focus runs pretty well, but after it has been driven a good while on the highway, it can be trouble if one shuts it off for a few minutes while doing an errand. When re-started, it will not idle. The only solution is either to wait a good while (1/2 hr, maybe?) or keep the engine speed up, well above normal idle. This isn’t easy; yesterday, I stalled and re-started at least a dozen times trying to get home. The engine will die whether in gear or not.

Somewhere I read that there’s a device affecting idle speed that can fail if under-hood temps get high enough. The writer suggested heating it with a hair-dryer when the engine itself is less warm.

Do these systems ring a bell with anyone, and can you describe what successfully solved the problem?