FLT INSTRUCTOR AND STUDENT EXPERIENCE THROTTLE STUCK AT IDLE WHILE PRACTICING STALLS.

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WHILE ON A NORMAL FLT INSTRUCTION FLT; DEMONSTRATING AND PRACTICING PWR-OFF STALLS WITH A PVT PLT STUDENT; THE STUDENT WAS RECOVERING FROM THE THIRD PWR-OFF STALL. SHE LOWERED THE NOSE AND TRIED TO APPLY FULL PWR. HOWEVER; THE THROTTLE WOULD NOT MOVE FROM THE LOW POS. I; AS THE FLT INSTRUCTOR; TOOK THE FLT CTLS AND TRIED TO DISLODGE THE THROTTLE; HOWEVER; IT WOULD NOT MOVE -- IT FELT AS IF THE THROTTLE LINKAGE WAS BINDING. I NOTICED THAT THE RPM WAS STABLE AT 1000 RPM; SLIGHTLY ABOVE IDLE; PROVIDING ME WITH MINIMAL PWR. I ACTED TOWARDS THE SITUATION AS IF IT WERE A COMPLETE ENG FAILURE; PITCHED FOR BEST GLIDE SPD AND CHOSE A FIELD TO LAND ON APPROX 1 MI E OF OUR POS. AFTER ENTERING A HIGH DOWNWIND FOR THE FIELD; I CONTACTED TWR; DECLARED AN EMER; AND SQUAWKED 7700. TWR GAVE A WIND READOUT AND STATED THEY HAD OUR ACFT ON RADAR. THE FIELD WAS APPROX 1 MI IN LENGTH AND WIDTH WITH MINIMAL VEGETATION; HOWEVER; IT WAS OUTLINED WITH PWR LINES. COMING OVER THE PWR LINES; AND ONCE PAST THEM; I PULLED OUT THE MIXTURE TO ELIMINATE ANY THRUST FROM THE SLIGHTLY HIGHER THAN IDLE PWR SETTING AND DROPPED FLAPS TO 40 DEGS. USING A SOFT FIELD TECHNIQUE; I WAS SUCCESSFULLY ABLE TO LAND THE ACFT WITH NO HARM TO EITHER MY STUDENT OR I; AS WELL AS NO DAMAGE TO THE ACFT. I THEN CALLED TWR ON THE PHONE TO INFORM THEM OF OUR SAFE LNDG. FOLLOWING THIS; I CALLED THE COMPANY CHIEF INSTRUCTOR WHO THEN CAME WITH 2 COMPANY MECHS. AFTER AN INSPECTION OF THE THROTTLE CABLE THE MECHS DETERMINED THAT THE CABLE NEEDED TO BE REPLACED; HOWEVER; THEY WOULD BE ABLE TO POS THE CABLE FOR THE FLT BACK TO ZZZ SO THAT IT WOULD BE SAFE FOR FLT. AFTER CALCULATING THE WT AND BAL; TKOF PERFORMANCE; DETERMINING MY COURSE OF ACTION SHOULD ANOTHER THROTTLE PROB OCCUR DURING MY DEP; AND ARRANGING A RIDE FOR MY STUDENT; I AS THE SOLE OCCUPANT OF THE ACFT; PERFORMED A SOFT FIELD TKOF INTO THE WIND OUT OF THE FIELD. THE FLT BACK TO ZZZ LASTED 0.3 HRS AND WAS UNEVENTFUL. I THEN LANDED SAFELY AT ZZZ WHERE THE ACFT IS BEING TENDED TO FURTHER.