What was found
IAW - FLIGHT 2758, THE CREW REPORTED THAT ENGINE 1 SURGES IN FLIGHT. CRUISE THRUST N1 FLUCTUATES =/-15 PERCENT WITH AN ITT RISE AND FALL; N1 REQUEST CARAT ALSO FLUCTUATES =/- 15 PERCENT, AND THE CRZ THRUST SETTING AUTO ADVANCED TO TO1. ENGINE 1 FADEC AUTO ALTERNATED TO "A", AND AFTER RESET TO FADEC B ENGINE INDICATIONS REMAINED NORMAL. THE AIRCRAFT RETURNED TO IAH WHERE IT LANDED WITHOUT INCIDENT. MAINTENANCE REMOVED AND REPLACED FADEC 1A, OPERATIONALLY TESTED WITH NO DEFECTS, AND THE AIRCRAFT WAS APPROVED FOR RETURN TO SERVICE.