What was found
AFTER LEVEL OFF FOLLOWING AN UNRESTRICTED CLIMB TO FL 380, LT ENGINE BEGAN TO SURGE +- 2 PERCENT N1 (APPROX). ENGINE SYNC-ON. EGT, N2 AND FUEL FLOW WERE ALSO FLUXUATING WITH FUEL FLOW =- 50 TO 75 PSI. ENGINE SYNC TURNED OFF WITH NO CHANGE (STILL FLUXUATING). BOTH ENGINE ANTI-ICE SYSTEMS WERE TURNED (ON) AND ABOUT 3 SEC TO 1 MINUTE LATER ALL ENG PARAMETERS RETURNED TO NORMAL (ENG. TREND LOG TAKEN AND FAXED SEPERALY) SHORTLY BEFORE DECENT ENG. A/I TURNED OFF (STILL AT FL 380) ENGINE AGAIN BEGAN TO SURGE. ENG A/I TURNED BACK (ON) ALL PARAMETER RETURNED TO NORMAL (FUEL WAS SUMPED PRIOR TO FLT CLEAN). DURING CLIMBOUT AND AT LOWER ALTITUDES (OAT >10 DEGREES C) ALL ENG PARAMETERS NORMAL