So I took a newly delivered MTH BNSF ES44AC 20-20510-1. Up to about 8 miles per hour the movement of the engine is very jerky. I cleaned the wheels. I noticed one of the wheels wasn't pushed on to the axle all the way which made for iffy gear mesh so I corrected that. All of my other engines are operating just fine. I cleaned off the tach wheel on the back engine. I don't know what else is left. What I have read it could be a bad tach wheel sensor.
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I should also add it's jerky in both directions
If convenient to hook to a conventional-mode train transformer you can turn off speed-control (Whistle-Bell-Bell followed by double-horn blast acknowledgement). This takes the tach wheel sensor out of the equation and the motor simply operates based on track voltage the old-fashioned way. You can run the engine fwd and back under voltage control and confirm the gear meshing, transmission, etc.. is smooth for slow speed operation. This will isolate if the issue is with the tach system.
That is, if the jerkiness is still there in conventional with speed control disabled you might still have a mechanical issue.
If the jerkiness goes away for slow speeds then it could be something in the tach system. For example, even with a cleaned tach striping check the distance (thickness of a dime) between black sensor chip and the flywheel striping...and insure sensor chip is centered and aimed in the middle of the flywheel stripes.
There have been threads discussing slow-speed jerky operation on MTH diesels that require some fussing with motor alignment in the wheel-trucks requiring, in some cases, shimming the motor to improve gear meshing (for example). Can get a bit involved and hopefully you don't have to go down that path...
My experience with jerky running is that it's usually mechanical, so as Stan says, eliminate that first.
Did you buy the engine new or used? I bought an engine used and the tach sensor plug-in came loose, almost out, and gave me similar trouble, so see if that might be your problem.
Lee Fritz
brand spankin new $420 engine.
Is there a traction tire off a wheel perhaps jammed behind the truck?
It sounds like you may have had the shell off, That would have been a good time to check out for anything binding by turning the fly-wheel with your fingers while holding the engine off the track with your other hand.
I don't think the timing tape and reader spacer reading would cause this however dirty track and being a brand new engine might. A little lube on the center rail roller pin might help. Maybe even give it a good run.
Did you break it in? I have had that problem before and let it run for about 20 scale miles at about 15 scale miles per hour and it smoothed out just fine at slower speeds.
Just a suggestion. Good luck! Paul
Before this I didn't run it much. So I will put some miles on it. I narrowed it down to the front motor by turning the flywheel. I removed the screw that holds the motor to the truck. The wheels and gears moved nicely and the motor spun freely. The resistance has to be coming from the worm gear.
Check how the idler gears meshes on the Truck. I have had several 2R-3R PS-3 that the tolerance is too loose and I had to shim the bearing with shim stock to engage teeth more. The Base of the truck comes off with three screws and the roller. G
It's definitely the worm gear from the motor to the truck. I did a 30 mile break in period. No change. Then I loosened the screw that attaches the truck to the motor just a little bit. All is fine. So I will have to shim the motor from the truck.
I've had several MTH trucks that I had to shim very slightly to get a proper mesh of the worm gear.
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