I know that this topics has been covered by many threads, but i can't seem to find a situation that matches mine. From what i've read, high idle is a common problem for a z32. I just got mine and it idles at around 1500-1600 normally. I was told it was the TPS sensor and it wasn't. Not a vaccum leak. At times it will surge quickly from 1500-2000 and back and forth a few times then stop. The more i drive it, the more it seems to surge randomly after i have it let it in neutral. Any opinions? One more thing. I checked the radiator and it has some old nasty rusted water in it. I need to flush it with radiator flush and refill it, but would that have anything to do with it?

 

i have a 90 z32 tt and ive noticed the same thing. i drive 30 minutes to work and it idles fine on the way but when i get there it likes to sit around 1k and wont go down. im not sure what could cause this. but im going to try and flush the system like you suggested to see if that helps