My Kuor3's idle Issue

I own a Cuore that has a K3 swap, its been a good car except it has an issue at idle, in that it idles at around 1700rpm.

Now I need to stress how much this annoys me and how hard I have tried to investigate it.

When I purchased it, I was tempted not to because of the high RPM, besides the high rpm however the car has never let me down.

The high idle some days can turn into idle hunting which is even worse!!

What have I tried?

  • Replace all vacuum lines, sounds kinda like a leak at certain RPM
  • Cleaned throttle body
  • Removed sensors and replaced (ISC and MAF)
  • Tested with soapy water and carby cleaner for sign of bubbles or idle skipping

Here is the really messed up part though
Whilst the engine was in the white car I started it, short run because the radiator was trashed but to test the idle, it was around 1100rpm, which is normal before its warm.

So I thought ok ill just put the engine in from the spare gtvi I had, which I did annnnnnnd
It idles at 1700rpm with the occasional idle hunt…

The engine did idle fine in the GTVi.

I then swapped ECU and Immobiliser… Still idles high… and have had two mechanics and 1 sparky scan tool it… none of them have been able to figure out the fault.

Went thourgh similar with my Subaru Liberty wagon with a fast idle but no hunting. In my case it was the throttle body. More than just a clean. Old one did pivot fine/smooth but at one stage - all of a sudden - decided to iddle really fast. Like you changed sensor, vacuum check (first thing I did) and a thorough clean. Problem seemed to be in the air by pass.

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I’ve had alot of drama’s with air locks in the cooling system causing a high idle which could be the throttle body like Mr gormsby said. I know with a charade the coolant flows through the throttle body which is the highest point in the cooling system and the cold start is controlled by it.

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have you tried the coolant bypasing the throttle body? I tried with my mira and charade (he-e). I got more hunting when I did but the charade always had a hunt issue with coolant trapped. In the past I had done this bypass with various other cars with no issue but with dais I always got the hunt?
Since I have seen other people do the bypass on mira’s and have no drama’s at all.
The injectors havent been de capped or anything and its getting too much fuel? (dont think it would be)
o2 sensor? map working ok?

Im just throwing out some random things that you may have other parts laying around to try.

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Currently have a bypass setup but it’s not been any help.

I believe it has to be in the wiring although I’ve tried twice to confirm its correct …

What gets me is I have swapped from another car

  • engine
  • engine loom
  • ecu and immobiliser

The problem did not exist in the donor but has now existed twice in the kuor3.

Maybe it is in the cooling system? I rarely but sometimes here almost running water under the dash on a cold morning… There is no leaks in the system though, the temp is nice and stable.

We have scanned the ecu with a quality Toyota scanner not ebay junk and it complains of nothing…

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Sounds like coolant, it’s normally in the heater core you can hear it bubbling under the dash. I’d try a good bleed of the cooling system and see how it goes.


Does anyone know if the gtvi heater box is the same as a Cuore? I’m not at home right now to check… But considering it is pretty much the only part of the puzzle I have not swapped over…

The bypass to the throttle body made zero difference and I think it may be the problem but then I think I swapped engines and the issue still exists so maybe it is in the bubbling heater core.

bypass the heater to see and you will find out if it is.just dont do it in cold weather so hurry up and check.
I have had many days where I used to have a blanket in the car as it was that damn cold.


Bit off topic but in the summer of 1989 I bought a Porsche 914 for the short time in lived in Michigan. I’d never seen the snow and had no idea what was coming. Winter there with no heater meant dressing to look like the Michelin Man. Must say even in minus 30c the 914 started every time.

Back to the issue, it’s not something like a bad earth is it? What are the variables or things different between the engine’s old and new home? Sticky throttle cable (yeah a bit obvious and am sure you’ve ruled that out), bad pcv, vacuum hose check again,…or what effect does covering the throttle body opening have?

I’d try a simple coolant bleed first. Turn the heater on and let the car get up to temp with the radiator cap off. I usually squeeze the radiator hoses to help push any air out aswell.

My drive way is on an incline and if I park nose in its a perfect setup to bleed the system, unfortunately I tried yesterday, heater on and let it warm up until thermo fan turned on and it started hunting… No different.

I got a hose joiner today so will try bypass the heater box, I will also return the lines to the throttle body

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All earth leads have been changed as sparky thought that might be a cause.

All vacuum lines changed and checked over and over as at around 2000rpm on light throttle I swear there is a leak.

Covering the throttle body around 95% produces a loud squeeky sound… Covering 100% causes engine to stop.

The only thing not swapped is the brake booster but when removing this hose with engine off there is vacuum pop, and I’ve tried just blocking this hose and no change.

Soapy water and carby cleaner show no signs of vacuum leak

I am so stumped. Will be trying bypassing the heater box Tomorrow and have another throttle body sensor to try (the one the coolent flows through)

You said you cleaned the iscv didn’t you?

Cleaned and replaced :frowning:

So today I did the heater box bypass, returned the coolent lines to the throttle body and gave it all a good burp.

Sadly this didn’t resolve my problem :frowning:
I have a spare engine and have confirmed I have replaced every hose possible…


Have tried changing the coolant temp sensor or the air intake sensor?
I think this is a sensor related issue, it may pay to swap out the engine loom and sensors.

I swapped
Engine loom and ecu…



i think it just needs that turbo engine in it. Im sure that will fix it lol :wink:

Might be the only way haha

Just worried about it being the same outcome…

lets hope not