Lionchief quirks.

The lights are normal as the motors turn into generators when pushed.

WOW! Our trains actually have Dynamic Braking! What will they think of next...

I guess this is regular LionChief, and not LionChief Plus, correct?  Also I'm guessing your loco has the small motors mounted in the trucks, and not the vertical motors found in higher-priced locos.  What's the product number?  That's always a good place to start.

How did it run before you started modifying it?

I never tried it with the Bluetooth prior.   It ran fine before and after with the remote, and runs fine with the Bluetooth with the only thing being when you throttle down with BT the sudden burst of speed, and then it  resumes slow down.  

It's an engine out of a starter set that I picked up brand new cheap. Don't have the set number, but the engine is bnsf RS3  #3717.    It's the engines Lionel is currently using and it'starter sets with RS3s w/bt.

Lionchief doesn't have speed control, which may be contributing to your second observation, or it could be due to the additional motor that is not part of the design.  Shouldn't be experiencing sudden changes in speed (except on tight curves, perhaps) without changes in control settings.

I have no experience with "regular" LionChief.  I guess the on-board circuitry is chopping the sine wave to modulate voltage to the motors.  Obviously the second motor doubles the back-EMF.  But if there's no closed-loop feedback speed control, I don't understand why that would matter.  Since we're just fooling around, you could also try wiring the motors in series.  It's all fun and games until someone lets the magic smoke out ;-)

Honestly it sounds like a software issue.  If you're using a smart phone, maybe you could try a different brand (Apple vs. Android, etc.)  Or--do "regular" LionChief locos respond to the Universal Remote??

I did wire the motors in series. I was going to do it in parallel, but didn't want to take a chance with the extra current damaging the board.  

It works fine with the regular lionchief remote that came with it.

One more question... what are you using to power the track?  Is it turned all the way up?

Sometimes if you have an electronic transformer chopping the sine wave to produce track voltage, and the on-board circuitry chopping the sine wave, you end up with some kind of electronic interaction that starves the motor or produces undesired effects.

I still think it's an issue with the smartphone client software.

Dual motors on a LCBA are designed to be wired in parallel, NOT in series. Plus each motor needs the 22uH 1A inductors on the + and - side.

Right now I'm just using the DC wall wart on a simple loop. 

Dave, I did use  22uH 1A inductors on both sides.  

Maybe I'll tinker with tomorrow and swap the wires to parallel.  

I wired in series because I was concerned about the higher current harming the board.

Here's my final findings on this. I fiddled around today and did a couple of things. First thing I did was try a "BW" 80 (not CW) Transformer. No change. I tried a post-war ZW as well. No change.  Instead of hooking the motors back up in parallel as Dave suggested, I just disconnected the second motor and tested it as it came originally with the one motor. Same deal.   Given that, my conclusion is it's either a glitch in this engine, or something with the software.  It doesn't really matter for me, because if if you ever see my previous input on Bluetooth, I'm not a fan. I just thought I would give it a try. I do like it for setting the sounds, but prefer the remote for operation.