CARGO WDB HAS AUTOPLT AND AUTOTHROTTLE PROBS. ALTDEV HDG DEV; SPD DEV.

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WE WERE BEING VECTORED FOR AN ILS TO RWY 18R (COURSE 176 DEGS) AT ZME. APCH VECTORED US THROUGH THE LOC FOR RWY 18R ON A HDG OF 150 DEGS. TO INTERCEPT; WE WERE THEN TURNED TO A HDG OF 200 DEGS. WE WERE 1 TO 1 1/2 MI E OF THE FINAL APCH COURSE. AFTER ROLLING WINGS LEVEL ON HDG 200 DEGS; I SELECTED VOR LOC MODE ON THE FLT CTL PANEL. THE AUTOPLT STARTED A 25 DEG BANK TO THE R. AFTER REACHING A HDG OF 230 DEGS AND STILL TURNING; I DISCONNECTED THE AUTOPLT AND TURNED L FOR A MORE REASONABLE INTERCEPT ANGLE. AS I GOT ESTABLISHED ON THE LOC; THE AUTHORITIES; WHICH HAD BEEN MAINTAINING FINAL APCH SPD; (135 KTS) ADVANCED TO LIMIT. THE AIRPLANE GAINED ABOUT 300 FT BEFORE WE WERE ABLE TO DISCONNECT THE AUTOTHROTTLES AND LOWER THE NOSE OF THE AIRPLANE TO RECAPTURE THE ALT. AT NO TIME WAS ANY KNOW AUTOFLT PARAMETER REACHED THAT WOULD TRIGGER THE 'SELF PROTECTION' MODES. EVENTS DESCRIBED ARE UNEXPLAINED; AND MAINT CHKS OF THE AIRPLANE WERE NORMAL. I WAS PREPARED FOR THE LOC CAPTURE PROB; BUT I WAS NOT PREPARED FOR THE AUTOTHROTTLE EVENT; AND SHOULD HAVE BEEN MORE AGGRESSIVE CORRECTING THE ALT CHANGE.