I had problems of that sort come and go for years with my first Renix, 87. I have found a bunch of things that cause it. I once found that a fixed, working Renix, would start with a very high idle if you had the jeep in Run for several minutes with the engine off (running say the radio, or doing electrical tests), and then go back to normal by just turning the engine off, waiting 10 seconds, then restarting it. In your specific case it could be:
1) Junk in the throttle body sticking the pentle in the IAC to the throttle body as already mentioned.
2) Funky, variable grounds (loose, dirty...), on the TPS, or other sensors.
3) Hot sensor and controller (IAC is a controller part, not a sensor) wires (versus grounds) that have connector problems. C-101 bulk head connector connections that are too loose, or corroded, same goes for fuse box, etc.... C-101 is on the firewall near the Master Cylinder.
4) You have already covered the IAC and TPS.
5) My floor mat can get stuck under the gas peddle and cause a high idle! Talk about random!
6)The Air temp sensor in the Intake manifold can go bad in a way that causes high idles, sometimes randomly. Ask me how I know!
7) And the best one of all, the funnest to trouble shoot,.......but wait for it...........
ALL of the above!:soapbox: