ACR X POSSIBLE LTSS FROM ACR Y. POSSIBLE SYS ERROR.

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ACR X NBOUND OVER RWY 22R FINAL; ACR X DEPARTED RWY 14L. NO TFC FROM SE TO PREVENT ACR X FROM PARALLELING RWY 22R FINAL AND CLBING TO GET ABOVE THE FINAL. I ASKED FOR A GOOD RATE OF CLB AND IT APPEARED ACR X WAS EXECUTING THE INSTRUCTION. WE USED PREARRANGED COORD FOR OUR CLBS AT ORD; SO IT IS NECESSARY TO INSURE CLBS IN LARGE GAPS SO VERT IS NOT NECESSARY. ACR X IS OUT OF 3400 FT AND ABOVE THE 'A' TFC SO I TURNED HIM TO 340 DEGS AND WORK OTHER ACFT. ACR Y WAS 7 MI IN TRAIL. APPROX 30-40 SECONDS LATER I LOOKED BACK AND ACR X HAD STOPPED CLBING OR CLBING AT A MUCH SLOWER RATE AND TURNING AT A VERY SLOW RATE. I IMMEDIATELY ISSUED A 290 DEG HDG AND ASKED AGAIN FOR HIS BEST RATE BECAUSE ACR Y WAS NOW 4 1/2 MI AWAY AT 5300 FT. THE OTHER CTLR INVOLVED CALLS TFC AND TURNS ACR Y TO 200 DEG HDG. HOWEVER; ACR Y RPTED ACR X IN SIGHT AND INSTRUCTS ACR Y TO MAINTAIN VISUAL SEPARATION BUT I DO NOT REMEMBER IF I TOLD MINE THAT VISUAL SEPARATION WAS BEING APPLIED BECAUSE I WAS BUSY WITH THE REST OF MY TFC. SUBSEQUENT VISUAL SEPARATION ALLOWED FOR 3 MI; 600 FT.