LTT CPR ACFT CREW HAS SMOKE IN COCKPIT FROM CTR PEDESTAL. USING CHKLIST FOR ELECTRICAL SMOKE AND REQUESTING DSCNT THE AUTOPLT WAS TURNED OFF. ATC WAS UNABLE TO DSND THEM AT THAT TIME AND A SHALLOW DSCNT OCCURRED WITH AUTOPLT NOT ENGAGED.

Narrative

WHILE ENRTE BTWN WHITE PLAINS AND TORONTO; WE EXPERIENCED SMOKE RISING FROM THE PEDESTAL AREA. IN ACCORDANCE THE ELECTRICAL SMOKE CHKLIST; THE AUX BUSES WERE TURNED OFF. THE SIC REQUESTED DSCNT FROM CTR. AFTER SOME CONFUSION AND BECAUSE OF AN ACR FLT WHO WAS IN CONFLICT; OUR DSCNT WAS NOT INITIALLY GRANTED. WE CONTINUED WITH THE CHKLIST AND THE PIC TOOK CTL OF THE AIRPLANE. WHILE BEING VECTORED FOR DSCNT AND CONTINUING WITH THE CHKLIST; WE FAILED TO NOTICE THAT WE HAD BEGUN A SHALLOW DSCNT. WE INADVERTENTLY DSNDED OUT OF OUR ASSIGNED ALT OF FL310. WHEN WE NOTICED OUR MISTAKE WE WERE AT FL255 AND HAD VIOLATED SEPARATION STANDARDS WITH THE ACR FLT. THE SMOKE WAS STOPPED BY TURNING OFF THE AUX BUSSES. WE LANDED AT THE GREATER ROCHESTER ARPT AND RECEIVED MAINT. I FEEL THAT WE OVERESTIMATED CTR'S ABILITY TO GIVE US AN IMMEDIATE DSCNT AND FAILED TO RE-ENGAGE THE AUTOPLT WHEN IT BECAME APPARENT THAT THEY COULD NOT. THIS LEFT THE CREW SPLIT BTWN FIGHTING SMOKE AND HOLDING ALTS. WE WERE FULLY AWARE THAT THE AUTOPLT WAS OFF AND WERE BOTH MONITORING OUR ALT AND STILL ALLOWED THE AIRPLANE TO DSND.