A MAINT FERRY FLT GOES BAD WHEN THE CREW IS UNABLE TO CORRECT A FUEL IMBAL SIT INFLT WITHOUT DAMAGING THE MALFUNCTIONING ENG; FL280 20 MI SW OF PHL.

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WE WERE ORIGINALLY SCHEDULED TO FLY THE DO328 FROM BOS TO CAE AS A PART 91 MAINT FERRY FLT EARLIER IN THE MORNING; BUT HAD ABORTED THE TKOF DUE TO AN ITT EXCEEDANCE ON THE R ENG. THE SAME REASON FOR WHICH THE ACFT HAD AN ABORTED TKOF THE PREVIOUS DAY. SEVERAL HRS AFTER RETURNING THE ACFT TO BOS MAINT; AND CONFERRING WITH MAINT AND THE CHIEF PLT; IT WAS DECIDED TO AGAIN ATTEMPT TO FERRY FLT TO CAE. ON THE SECOND ATTEMPT TO MAKE THE FLT; WE VERY SLOWLY APPLIED PWR TO AVOID EXCEEDING AN ENG LIMITATION; AND NEVER REACHED MAX TKOF THRUST BEFORE ACCELERATING TO V1. PWR WAS SET BTWN MAX CRUISE AND MAX CLB ALL THE WAY TO CRUISING ALT. THROUGHOUT THE ENTIRE FLT; THE R ENG WAS RUNNING 100-200 DEGS HOTTER; AND BURNING ABOUT 200 LBS/HR MORE FUEL THAN THE L ENG. WE AGREED THAT XFEED WOULD BE REQUIRED TO AVOID EXCEEDING A FUEL BAL LIMITATION ENRTE; DUE TO THE HIGHER FUEL BURN OF THE R ENG. JUST SW OF PHL; (SBOUND AT FL280; IN VMC BUT HAZY CONDITIONS) THE CAPT TURNED ON THE XFEED SELECTOR AND THE R ENG BEGAN BANGING AND SHUDDERING (VERY SIMILAR TO THE COMPRESSOR STALL IN THE SIMULATOR; THOUGH I HAVE NEVER EXPERIENCED A COMPRESSOR STALL IN ACTUAL FLT). THE CAPT IMMEDIATELY TURNED OFF THE XFEED; AND THE SHUDDERING STOPPED. WE THEN DECIDED THAT WE WOULD BE UNABLE TO CONTINUE TO CAE; SINCE WE WERE UNABLE TO CORRECT THE IMPENDING FUEL IMBAL SIT; AND BEGAN TO COORDINATE A DIVERSION. ROUGHLY 5 MINS AFTER THE FIRST SHUDDERING; THE R ENG BEGAN THE SAME SHUDDERING INTERMITTENTLY; THIS TIME WITHOUT THE XFEED OPERATING OR ANY OTHER INPUT BY THE CAPT OR MYSELF. THE ITT SPIKED TO 950 DEGS DURING THE SHUDDERING AND ENG VIBRATION ROSE SLIGHTLY FROM 0.1 IN/S TO 0.2-0.3 IN/S. WE FEARED AN IMMINENT ENG FAILURE; DECLARED AN EMER; AND PROCEEDED DIRECTLY TO IAD. I FLEW AS THE CAPT COORDINATED THE DIVERSION; THEN RETURNED THE CTLS WHEN HE WAS READY. THE SHUDDERING CEASED WITH REDUCED PWR SETTINGS IN THE DSCNT; AND WE DECIDED TO CONTINUE WITH BOTH ENGS OPERATING. WE MADE AN ESSENTIALLY NORMAL LNDG TO RWY 19R AT IAD WITHOUT ANY INDICATION OF ENG DAMAGE OR ABNORMALITY OTHER THAN THE CONSISTENTLY HIGH ITT AND FUEL BURN ON THE R ENG.