Wow Ed, I'm surprised!
My two stock PS3 steamers run smoother than anything I have. My frogs aren't powered yet and they glide right thru without any issues.
I do have issues like you're describing outside on my G scale. I believe the engines are not seeing power steadily enough so that they would stall at the first chance they got. I've done a lot of work to smooth out all the track power issues like switches that aren't carrying power thru all their rails. Dirt and corrosion outside take their toll on things that started off working fine.
Anyways, I'm betting that G is right about the electronics being sound. I'd bet it's either the coating or even a problem with the tether? I keep mine connected as much as possible. I've heard others complain heavily about them.
If you decide to sell the PS3 guts, I would be in the market. It's tough for you because the upgrade kits are very economical now.
