My engines have been slowing down, stopping, starting, speeding for a lap or two, and then repeating the process on my outer loop. I had decided that it was a feeder a problem and was going to either run a new main power wire to the feeders or connect the feeders to an electrical bus. Somebody here said to do "the easiest thing first". So I scrubbed the track down with Simple Green.
WA-la, problem solved. I had no idea that the it was that simple. I used rubbing alcohol just before Christmas and thought the dirty track problem was history. Apparently not so. I used an old sock and it came up black when I was finished.
Now the root of the problem must be excessive oiling of wheels and rollers. Let that be a lesson to me. I consider it all a part of the fun of the hobby but I'd rather just run the trains.
Anyway, whoever said it - thanks!