To all who posted suggestions, thank you very much! I tried them all. Unfortunately despite some temporary relief nothing solved the problem and I remain at 2

To all who posted suggestions, thank you very much! I tried them all. Unfortunately despite some temporary relief nothing solved the problem and I remain at 2800 RPM with 93% idle CPU, though now without TurboBoost! :-) On the positive side, the offending MBP now has its apple-face to the wall and the fans seem slightly quieter that way. Next I will look into locking it in a refrigerated safe.