Interesting PS2 problem using a donor engine PS2 board

 I might  check the timing tape / reader spacing,(should be about the thickness of a dime) and also make sure the motor leads are not touching motor casing .

When you say " it moves off pretty fast"  Does that mean full tilt?

I'd say it is not a runaway condition, its more like 25MPH....almost like it might perform in conventional mode at 12volts....

How the tape /reader spacing?   I don't think it's going to help but how about a feature reset... Menu/ Advanced/ reset engine/ feature reset. (it's easy to try)

Appreciate your help!  The tach spacing is ok using the dime as a feeler gauge.  I did some more trouble shooting and was pretty surprised at the following test:

I plugged another working UP Railking PS2 tender (#4002) into my #4017 engine and experienced the same issue of no running sounds and "fast acceleration".  I then plugged the #4017 tender (the one with the donor PS2 board) into my #4002 Railking big boy and it ran as expected with no problems.  So I'm guessing that something is not right with the #4017 engine components itself.  As stated before, the tach board clearance is good and I don't see any obvious wiring/issues with the components in the engine shell....) I've even tried running #4017 without its shell...Obviously something caused the original PS2 board to short/fail in the first place.  Oh well, it was worth the attempt....Maybe I'll donate the big boy to my fictitious layout city park for display.  :-)   

Seems you've narrowed it down to the engine,,, Must be a wire shorting out or touching something it shouldn't engine side . Hopefully one of the tech guys can give you  some leads....  good luck.

Think I'm going to swap out the tach board with another donor since all the symptoms seem to be motion/speed related....Thanks again!

There was another very similar thread not too long ago...The problem turned out to be,, shorted wire in the 10 pin connector engine side... The wires were actually burnt .  I see if I can find the thread.   yep try the reader.

Success!  The donated tach board swap out did the trick.  It was good practice for my rusty soldering and troubleshooting skills too.  Now #4017 can avoid the scrappers torch.