Bad Pickup Roller??

I have a Weaver RS-11 diesel that will stall on my Lionel 022 switches, not all, but enough at slow speeds. The track is clean and so are the rollers. Track connections are good. I checked for loose wires and found 1 that was loose from the sounds control knob. I soldered that and couldn’t see any others loose. Didn’t help. I do notice 1 roller sparking for a lot of the time. Could this be bad or what else??

Thanks in advance.

Just a quick & simple check of the p/u rollers is to put a short strip of electrical tape on a center rail, straight section preferrably, then slowly drive the loco onto the tape. If it stalls that pretty much indicates that only one p/u rolleris operating correctly. Turn the engine on it’s side and use a little contact cleaner, WD-40 etc on the roller pin & inside of roller while turning it with your finger tips. That should help to clean anything out that mite impair the conductivity, afterwards if you have any put in a couple of drops of a conductive lubricant.

Hope this helps.