A320 ACFT ON APCH AND APPARENTLY NOT PROPERLY SET UP FOR THE APCH WAS GIVEN A GAR BY THE APCH CTLR. THE GAR WAS INITIATED; BUT WITHOUT TOGA THRUST UNTIL THE CAPT RPTR TOLD THE FO TO USE TOGA. AT THAT TIME; UNKNOWN TO THE FLC; THE ACFT CHANGED MODES AND IGNORED THE PREVIOUS INPUTS SET INTO THE FMGC.

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DUE TO DETERIORATING WX CONDITIONS AND ABNORMALLY HIGH WINDS AT ALT VERSUS ON THE GND; DTW APCH CTL DIRECTED A GAR: MAINTAIN 3000 FT; TURN L 220 DEGS AND SPD OF 170 KTS. I RECOMMENDED TO THE FO TO GO TO THE TOGA THEN BACK TO CLB TO RESEQUENCE THE FMGC FOR THE ADDITIONAL APCH. THE ACFT STARTED CLBING; DISREGARDING THE 3000 FT FCU ALT. I DISCONNECTED THE AUTOPLT AND TOOK CTL OF THE ACFT TO RETURN IT TO 3000 FT. THE FO SAID WATCH YOUR AIRSPD WHICH WAS RAPIDLY INCREASING. THE FMGC IS SUPPOSED TO HONOR THE APCH SPD (140 KTS) OR FCU SELECTED AIRSPD (170 KTS) WHICHEVER IS HIGHER. IT DISREGARDED BOTH. I DISCONNECTED THE AUTOTHRUST AND RETARDED THE THRUST LEVERS. APPARENTLY THE FMGC STUCK IN THE GAR PHASE EVEN THOUGH THE THRUST LEVERS WERE IN THE CLB DSCNT. IN RETROSPECT WHAT WAS UNSETTLING WAS HOW LONG IT TOOK TO RECOGNIZE THE PROB THAN DEAL WITH IT. IN KNOW OUR FMGC'S HAVE BEEN EXPERIENCING NUMEROUS PROBS WHICH HAVE GOTTEN WORSE OVER TIME. I DON'T KNOW IF THIS HAD ANYTHING TO DO WITH THE ABOVE PROB.