CTLR RUNS COMMUTER ACFT TOO CLOSE TO ANOTHER ACFT BEING WORKED BY AN ADJACENT CTLR.

Narrative

THE ACFT UNDER MY CTL WAS A COMMUTER LTT X AND THE ACFT BEING CTLED BY ANOTHER CTLR WAS CGA Y; AN SMT. THE AIRSPACE AT PORTLAND TRACON (P80); OR; WAS SPLIT INTO 2 SECTORS; NEWBERG ('U') AND DEP ('D'). I WAS WORKING THE 'U' SECTOR. THE SPLIT CONSISTED OF BASICALLY SPLITTING ALL OF P80 AIRSPACE IN HALF FROM E TO W; WITH THE EXCEPTION OF A PORTION OF THE AIRSPACE TO THE W OF THE ARPT WHICH WOULD NORMALLY BE OWNED BY THE PORTLAND FINAL ('F') CTLR WOULD NOW BE OWNED BY THE 'D' SECTOR. THE NORMAL PROC IS FOR THE 2 CTLRS ('D' AND 'U') IN THIS CONFIGN TO SHARE THE 'F' AIRSPACE. I WAS WORKING THE 'U' POS AND I CLRED LTT X FOR A VISUAL APCH TO FOLLOW CGA Y. AT THE TIME THE CLRNC WAS ISSUED HE DID NOT SEE CGA Y; BUT I ANTICIPATED THAT HE WOULD. I BELIEVE THE VISIBILITY WAS CLR. THE PROBLEMS AROSE WHEN THE 'D' CTLR REMINDED ME THAT MY ACFT WAS GOING TO EAT UP THE SPACE BTWN THE 2 ACFT BECAUSE HIS CGA HAD SLOWED DOWN CONSIDERABLY. I BELIEVED THAT THE LTT X HAD SEEN THE CGA BY NOW AND JUST HADN'T SLOWED TO FOLLOW. BUT THAT WAS NOT THE CASE; AFTER GIVING AN UPDATE ON THE TFC; LTT X WAS TO FOLLOW; HE REPLIED THAT HE WAS LOOKING. I SLOWED THE LTT X DOWN TO MATCH SPDS WITH THE CGA. BUT THE SCENARIO GREW WORSE EVEN THOUGH THE LTT X DID GET THE CGA IN SIGHT BECAUSE THE CGA OVERSHOT HIS FINAL AND HAD TO MAKE A WIDE TURN BACK TOWARD THE ARPT. I FINALLY TURNED THE LTT X OUT AND VECTORED HIM BACK FOR ANOTHER APCH. 2 CTLRS WORKING ACFT ON SEPARATE FREQS THROUGH THE SAME AIRSPACE AND ALWAYS TRYING TO SECOND GUESS WHAT THE OTHER GUY IS DOING. FOR IF I HAD BEEN WORKING BOTH ACFT; THEN THIS SCENARIO WOULD NOT HAVE HAPPENED; BECAUSE I WOULD HAVE ENSURED THAT THE LEADING ACFT (THE CGA) WAS GIVEN A SPD TO MAINTAIN AND THE FOLLOWING ACFT (LTT X) WAS SLOWED TO MATCH UP FURTHER OUT. FOR AT THE TIME; THE CLRNC WAS ISSUED TO LTT X THE SPDS WERE MATCHED. HAVE 1 CTLR OR THE OTHER OWN THE AIRSPACE AND WORK THE AIRPLANES WITHIN THAT AIRSPACE. IF THIS BECOMES TOO BUSY; THEN THE FINAL POS SHOULD BE OPENED.