Cadillac Repair: 85 seville 4100 idle surge and stalls when warm, vacuum lines, vacuum leak

Question
I appreciate what you do here. Car starts fine and runs smooth during warm up. Once warm, idle starts to surge and then it stalls. I can see the ISC working back and forth. Where do I start troulbeshooting this since it's wired to the ECM? I've been studying my Chilton manual but there's so much to go through. No check engine light BTW. Thanks in advance.

Answer
A VERY important piece of information: TRASH that Chiltons manual as it will get you into more trouble trying to diagnose problems due to it's lack of COMPLETE information.

A surging ISC motor is usually caused by an intake manifold leak and or a vacuum leak in one of the vacuum lines.

Try spraying CARBURATOR CLEANER around the intake and on the vacuum lines to see if the engine changes speeds.

Does the ISC make any clicking noises when it is doing this or when you first turn ON or OFF the engine ?.