High Idle that resets after ignition off/on. CG10DE Pre FL 1994.

Hi all.

I am chasing an issue where only when the engine is hot during a run, coming to a halt such as traffic lights, the idle will be noticeably higher, this also in turn reduces engine braking. Turning the ignition fully off and back on resets the idle to the normal level.

My car uses ODB1 so I am not sure how to actually get a fix on the sensors and what is wrong, or is their a clear indicator to the culprit?