ADVTECH MLG FLC ENCOUNTER RUDDER PEDAL ASSEMBLY PROBLEM ON TAXI-OUT AT ATL.

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DURING FLT CTL CHK OF RUDDER PEDALS (ON GND IN ATL); THE CAPT FOUND THE R RUDDER PEDAL WOULD NOT MOVE MORE THEN 2- 3 INCHES. L PEDAL TRAVEL WAS NORMAL; FO'S PEDALS HAD THE SAME PROBLEM. CONSULTING THE POM WAS NO HELP AS THERE IS NO ABNORMAL TO COVER THE SITUATION. DECISION WAS MADE TO RETURN TO THE GATE. UPON FURTHER INVESTIGATION AFTER SHUTDOWN AT THE GATE; THE RUDDER TRAVEL AND PEDAL MOVEMENT RETURNED TO NORMAL. WHEN THE ADJUSTMENT KNOB WAS PULLED ON THE CAPT'S SIDE; THERE WAS A PRONOUNCED POPPING NOISE FOLLOWED BY SOME LATERAL MOVEMENT TO THE RUDDER ADJUSTMENT KNOB WITHIN THE ASSEMBLY. WHEN A NEW ADJUSTED POS WAS MADE TO THE IN-AND-OUT MOVEMENT OF THE PEDALS; THE L PEDAL BOUND UP AND MOVED ONLY 1-2 INCHES FORWARD. MAINT DISCOVERED THE SLEEVE ASSEMBLY IMMEDIATELY BEHIND THE KNOB AND PEDAL ADJUSTMENT BRACKET WHICH ATTACHES TO THE ADJUSTMENT CABLE; HAD BOTH NUTS LOOSE. I BELIEVE THAT THIS CONDITION; BECAUSE OF ITS INTERMITTENT NATURE COULD HAVE EASILY NOT BEEN DETECTED. NEEDLESS TO SAY; THE POTENTIAL FOR DISASTER WITH AN ENG FAILURE AND THE NEED FOR RUDDER IN COMBATTING EXCESSIVE YAW COULD HAVE OCCURRED. SUGGEST THAT THE DESIGN OF THIS SYS BE REVIEWED WITH AN EYE TOWARD SOME TYPE OF PIN OR RETENTION WASHER ADDED TO PREVENT THE BACKING OFF OF THE NUTS ON THIS ASSEMBLY. I ALSO SUGGEST THAT THE REST OF THE FLEET BE GIVEN A ONE TIME INSPECTION FOR DETECTION OF ANY OTHER LOOSE ASSEMBLIES. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO. RPTR IDENTED ACFT TYPE AND STATED THAT HE HAS NOTIFIED THEIR COMPANY ABOUT THE POTENTIAL PROBLEM. HE ADDED THAT THE CAPT HAD SUGGESTED THAT HE SUBMIT A WRITEUP TO ASRS. HAS ALSO MENTIONED THAT HE NOW MAKES IT A PRACTICE TO CHK THE RUDDER ASSEMBLY BEHIND THE PEDAL FOR LOOSE NUTS.