Kitty train, a couple of thoughts. Is this your first Lionel engine with Odyssey control ? They do start out slow but should follow your throttle commands. I believe the engine you have is from the first run. The chuffing in these is all mechanical. No wireless tether. It could be as simple as the chuff switch. The smoke unit was a plunger type. Does the engine puff smoke ? The plunger could be stuck. I believe if that happens it can effect the chuff as the same linkage controls both.
My only other idea. EOB was very popular when these were made. They offered a drop in board that increased the speed steps. They accelerated very slowly no matter how fast you turned the throttle. The tach sensor could also control the chuff. Many upgraded just to get 4 chuffs per rev. . The factory gave it only 1. Not saying a conversion was done. Just putting it out there.
First off. What are you using to run the train. Transformer control or Command. These engines are pretty easy to take apart if you want to take a peek inside. Your problem lies in the engine. Not the tender.
