Yes, Dr. Lightninrod did make a good long-distance diagnosis - I was expecting to see the dancing banana icon on your post! The IAC valve seems to have been a major offender ( cpeapea, I will ask about having the valve replaced. Certainly, if it's going to cause this kind of trouble in the future I would rather just replace the valve altogether than have to worry about another episode like this) I will make sure that we keep an eye on it - also, RTKilla, I am going to go back next week and have a more in-depth discussion with my mechanic so that I can see more clearly what was in fact adjusted and tightened. Nothing was replaced that I know of but if it's matter of a specific fault I want to be able to pass that data on to you. It really shouldn't be so mysterious, but I wasn't there to witness the operation so I can't yet tell you precisely what was, in fact, adjusted.
Well, after suffering with the Jeep rental for two days I feel as though I have done my penance for the whole year, so I am looking forward to getting those winter tires off soon and driving on. Thanks again to everyone who helped me out here!
Susan