Fast idle issue when warm

[Jaynar71]

I recently finished an 1uz engine conversion into a Mercedes W202. It goes well and I'm really pleased with it. However there is one small problem/annoyance that I would like resolved!
A bit of background information... It is a 1uz from a 91 Celsior, also using the celsior autobox and running basically the standard wiring loom. The engine is standard apart from a set of headers and a free flowing exhaust.
The issue I'm having is this. When you start the car from cold, it will idle at a tad over 1000 rpm, which I'm assuming is correct, however as the coolant temperature rises, the idle speed doesn't reduce, even when up to operating temp (coolant at 75-80 degrees) But, if you stop the engine and restart when warm, the idle will reduce straight away to 650, and it will be ok until you do a cold start again.
There are no faults showing on the ecu, I have cleaned and serviced the IACV and replaced the ecu coolant temp sensor ( although it is a pattern part and not genuine Toyota)
As I said it's not a massive problem, but I would like to resolve it.
Has anyone come across this before.

 

[lill daddy]

Do the rpm's "hang" when you are driving too? do you find when coming up to a stop sign its still trying to push because of the extra rpm? I only ask as my conversion was doing this (and like yours would refire and be fine sometimes) but it turned out to be a sticky throttle body... gave it a strip and clean and has been mint ever since...you could "blip" the throttle and it would snap shut but if you just eased off the gas it would stay cracked open slightly...

Fyi I'm In Christchurch too... well Rangiora