Cadillac Repair: 86 sedan deville throttle switch, robert s arnold, throttle switch

Question
I HAVE A 86 SEDAN DEVILLE 4.1L ENGINE AND I HAVE A CODE 26 SHORT IN THROTTLE SWITCH AND CODE 30 IDLE SPEED MOTOR, THE ENGINE RUNS ROUGH WHEN COLD AND WILL STALL OUT, RUNS GOOD WHEN WARM. THINK I NEED A THROTTLE POSITION SWITCH?
ALSO I NEED TO REPLACE MY HEATER CORE I STARTED LEAKING SO I BY PASSED THE CORE. DO I REPLACE THE CORE FROM ENGINE COMPARTMENT OR UNDER THE DASH.
       THANKS FOR YOUR TIME
     ROBERT S. ARNOLD

Answer
Hi Robert, A tps will cause an engine to run  rough and stall but an ISC motor won't. You might have 2 bad parts but I would start by testing the tps with an ohmeter first and then replace it, clear the codes and see if the 30 returns.
The heater core is accessed from under the dash. If the a/c evaporator core went bad it is removed from under the hood. Bill