I recently bought a new Williams SD-90 BNSF Powered engine at a local train show.  When I first ran the engine on my layout (have Lionel Fastrak), it hesitates/jerks everytime it goes over a switch and the cab lights blink on and off.  I have another Williams SD-90 (BN) and it does not do this.  Any ideas why this is happening?  It is very frustrating.

Is the Williams 150 Watt transformer powerful enough to run a sound equipped train with lighted/smoking caboose on an 8x12 foot layout (single track)?