When I run my Thomas train around on my layout, sometimes it surges in speed and then slows back down almost like it is storing up energy and then releasing it.  The throttle is not changed to cause this to happen.  Any suggestions on how to fix.

I tried to play around the the CV settings and I found that my Percy Engine had a PWM CV of 0 and Thomas Engine had it at 180.  Not sure what the correct setting should be or if this has any bearing on the issue.

Thanks,
Michael Carney