engine with some legacy problems

I don't know if this is a new loco or not. But on newer LOCOS I have had several where the brake detail on the engine was rubbing the traction tires causing jerky operation. Solution to this is to get thinner tires. Bending the detail can result in broken parts. Easier than you would think. I would start there. As for the couplers try spraying some graphite lube right in the throat of the coupler and work it back and forth by opening and closing the coupler several times. Hope this helps. I would also check for dirty track or pickups. I assume you have also tried a reset

Do what Mike stated.  Those brakes and monster tires are a PIT_.  Try to hold the coupler when firing it to feel the coil buzzing.  If no luck with that, try below.

Open it up and pull and reseat the R4LC.  Pull and reseat the white Leoco plugs on the DCDS and motherboard.  The coupler plugs are the small 2 wire plugs. .  Reprogram the engine with your number and finish the reprogram with AUX-1-2.  If that does not bail you out give it to your guy who knows Legacy.  The fact of the coupler issue would tell you to start at the R4LC and those darn Leoco plugs. 

Make sure your running 16-18v for the couplers to fire.  I've had customers complain they couplers wouldn't fire and they were only running at about 14v.

Of course check for the buzzing feel as Marty indicated above.

The S-2 are great engines, if you are going to try and fix it yourself be very careful when removing the cab and body, they break easily. I suggest you take it to your local repair shop.

Bill

Thanks for all the suggestions.  Unfortunately nothing I could check without opening the engine seems to be the problem.  The track is at 17.1 volts.  There is plenty of clearance around all wheels and there is no buzzing in the couplers and even pulling on them when activating them will not open them. However the rear one did open once but that is all.  I also ran the engine several times around the whole layout at all speeds and it runs perfectly in the forward direction.  Reverse is very jerky and it usually just quits after a while and I have to reset it. (power down).  It is even worse if I am pulling a string of cars. 

So I am going to Legacy Station today to pick up some other cars I ordered and will let them open it up and see what they say.

Thanks again.