Cold start up -> car don't want to reach target RPM
 

Im quite a bit lost about this because my car was finally running flawlessly this autumn after a one year quest to get the car running in perfect condition . Then the very low tempereature has come ( i mean beetween 14F and -14F , below that , i usually do not take the car ) and the problem started .

First here are a quick mod list :
Evo 9 2.0 freshly built block , kelford 272 , ID 1000 , walbro 255 ,JB FP black ,JDL tubular manifold , spoolin up COP , every other bolt on etc etc .
So this is a midly modified car running around 450whp on 91 octane .
Car is Speed Density tuned by a very good local tuner , with tephra 7 and 3D SD.

So here it is . When i crank the car , i need to blip a bit the gas pedal to make a nice normal start up . This is not a problem . But then the car don't want to hold the targeted RPM set up in the tune VS the outside temp . So I need to hold the gas manually to like 1800rpm , then I depress gradually while the time pass and the car start to gain heat . If it's not heated properly and i let off the foot of the pedal , the car drop to 800rpm or so and will eventually die by itself . So I need to step up on the gas again .
I have to do this for around 3-4 minutes and then it's okay , the car idle like it should after .

This is quite confusing has I putted a brand new IAC valve 4 months ago and I adjusted the BISS screw with the SAS mode in Evoscan . Everything was done correctly and it was running fine after this .
This is not a tuning issue . 99% sure about this . My tuner is also a friend and he double checked everything . This is a mechanical problem as it was working properly and nothing has change in the tune .

What should i look for ??

Thanks guys

Just talked to the guy who build my block and he pointed me the fast Idle valve on the Throttle Body . This has something to do with the coolant temp if I understood correctly .

Could this make sense ?

There is no fast idle valve. Your fueling is likely pretty far off if you don't have a good base map to go along with the new cams and injectors. Which would cause it to die. What are your AFR's when it is idling low and dies? You also may need to adjust the biss screw. The car should idle very near your target idle rpm with the ISCV disabled via EvoScan

AFR are very rich when it does it , in the 10's . When does the FAIV was dropped off in our evo then ?
In SAS mode , the rpm is right on the target rpm , does not move at all as it was set up properly .
I opened up the BISS about one turn to help the car a bit , but this is not the right way to find my problem , it still doesn't idle properly when it's freaking cold at the start up . It's like putting a band-aid on it .

Our cars only have the ISV, and a TPS on the throttle body.

AFR in the 10's is why it won't idle. You need to fix the tune. Likely need to touch up the ISCV tables, and fix fueling at idle...