the motor doesn't by any chance have a capacitor wired across it?(one or more orange round or square disks) if it does, there's your problem.
I want to thank all that have replied. I finally gave up on the MRC modules. I totally rewired the loco, checked the motor, cleaned the wheels and it ran fine with very little amp draw under load. As soon as I installed the MRC module the amp draw went considerably up and the problems returned. I think the problem is with the modules. They would be OK for a childs layout that is basically flat with short trains. This experience has definately turned me off on MRC modules. I will just stay with soundless locos, except for any that I may purchase that already have factory sound modules, as I have been for over the past 40 years.