Standard loco tuneup procedures.
Clean the wheels and pickups. Does it pick up from all 8 wheels? If it's supposed to, you can test that by isolating any two wheels of a given truck by slipping a pice of paper between the wheels and track. If it's supposed to pick up power on all 8 wheels, and some are not, either because of a broken wire, bent pickup, or dirty pickup, the loco will be more sensitive to dirty spots on the track.
Clean the gears, and apply only a SLIGHT amount of a compatible lubricant (I use various Labelle products, grease for the gears and oil for the bearings).
If the motor it uses has a visible commutator and isn't a fully enclosed can motor, you can clean the commutator segments if they look more like a solid ring of black instead of a bunch of copper segments.
Slightly more work - remove the decoder and run it on DC and see if it runs smoothly. If it does, the decoder probably needs some configuration. If it doesn't run smoothly on DC after doing a tune up, it's not going to run smoothly on DCC.
Whatever you do - DO NOT connect DC power, even from a battery, to the motor terminals if the decoder is still connected. It WILL fry the decoder.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
I have a Model Power F7A engine. It was evidently converted to DCC a few years ago. Since received couple years ago it was always jerky, not smooth running. I just let it sit for years. Other than that everything appears good (lights, sound, DCC functions). Wondering if this unit ever ran real smooth?? Perhaps needs total cleaning of grease and oil? From initial searching it doesn't appear to be worth money or time. Any hope that it could become smooth runner?