A GULFSTREAM IV ON CLBOUT OVERSHOT ASSIGNED ALT DUE TO AUTOTHROTTLE MALFUNCTION.

Narrative

ON THE PREVIOUS DEP (AT ZZZ) WE EXPERIENCED THE R ENG ACCELERATING RAPIDLY ON TKOF; WHICH WAS INDICATING THE AUTOTHROTTLE WAS NOT WORKING QUITE AS IT SHOULD. SO WITH THE DEP AT SUS WE ELECTED TO PERFORM A RATED TKOF AND TO PLACE THE THROTTLES AT 1/2 THROTTLE WITH MAX BRAKING ACTION TO ENSURE THE ENGS WERE BOTH SPOOLED UP AND PROVIDING PWR. THE BRAKES WERE RELEASED AND THE AUTOTHROTTLES WERE ENGAGED. THE R ENG AGAIN ACCELERATED FASTER THAN THE L. AFTER LIFTOFF AND IN THE AFTER TKOF CHKLIST; THE R ENG TEMP ENTERED THE CAUTION AREA. THE AUTOTHROTTLES WERE DISENGAGED AND RETARDED TO NORMAL OPS. HOWEVER; WE WERE INITIALLY GIVEN 2500 FT RESTR ON TKOF; BUT WHEN WE DISENGAGED THE AUTOTHROTTLES; WE LOST THE ALT HOLD AND INADVERTENTLY EXCEEDED IT; BUT ARRESTED IT AT 3000 FT. THE CTLR VERIFIED WE WERE ASSIGNED 2500 FT; WE CONFIRMED THAT. HE RECLRED US TO 3000 FT. ALL INDICATIONS WERE THAT THERE WAS NO LOSS OF SEPARATION BTWN ANY ACFT. WE WERE MORE FOCUSED ON THE ENG PARAMETERS AND FAILED TO BE AS TIMELY AS WE SHOULD HAVE BEEN ON THE ALT.