What was found
ENGINE #1 DURING ENGINE START, ENGINE REACHED N2 44% - N1 11%, THEN N1 AND N2 ROLLED BACK WITH EGT DROP JUST PRIOR TO STARTER CUTOUT. EGT BOX WAS FLASHING WHITE DURING EVENT. GROUNDED - YES. PERFORMED B737-900 FIM 80-05 TASK 801, NO EXCEEDANCES OF EGT. PERFORMED EEC BITE PROCEDURE REF FIM 73-00 TASK 801, NO MAINT MESSAGES. PERFORMED BLEED AIR CHECK VALVE INSPECTION REF B737-800 AMM 36-11-02, FOUND FLAPPER PLATES BINDING. REMOVED AND REPLACED BLEED AIR CHECK VALVE REF AMM 36-11-02, LEACK CHECK GOOD. PERFORMED 2 SUCCESSFUL ENGINE STARTS.