Thanks for the info. I will probably put an overvoltage relay on tomorrow. Since I have been told that I should probably carry a spare anyway, it seems almost like a free one before taking the car to the local gurus. But I doubt that it will help. I think there is a rule that nothing cheap ever helps.
As far as the air mass meter, I did not think it had that much to do with idle (but you are the experts and that is why I asked you). The car runs great at any time except at idle in P or N. It has normal power and response. I just filled it and the mpg was within one mpg of the average over 65,000. It seems like a simple job to install. Does it take some adjustment after installation or is it a do-it-yourself job?
I have looked at the wiring because I have heard of the problems. It looks like new with no cracking or flaking of the insulation. Also, I do not get misfiring or rough idle, just a surging when in P or N. But I will certainly look at it if need be.
The check engine light is the far right one in the row of lights at the bottom of the instrument cluster. I never knew it was there it until it turned on but after looking, it does come on when the key is first turned and all the lights are checked.