I searched on HT and found similar threads about this but nothign 100% mimics the problem I am having. I have an 00 Si that I swapped a 99 jdm b18c into and the issue that I am having is the motor, on cold starts, will crank over start up and then die. However if I give it gas to get it going and hold it for like 5-10 seconds it is fine. Also, the idle is pretty unusually low on cold starts, not the 2kish idle that decreases over time. After a few minutes, the idle goes to normal (800-900rpm) but seems to drop pretty low on occasion AND when the radiator fan kicks on. It is kind of like the engine is searching for the right AFR or something to run at idle. Now, I used the rail and FPR from my Si on the motor (because I needed the EVAC mounting points), have a new distributor on it as well. Currently it has an open header because the testpipe hasn't come in the mail. I cleaned out the IACV and TB (which were dirty as ****) and I was not throwing a single code. I am sure the TB could use more cleaning, and swapping IACV from my b16 to this could work as well. Is there anything I am forgetting I can do to help alleviate this? One final note: when I started the motor up for the first time it had the smae issues but it was running pig rich, like there was air sitting on top of the coolant temp sensor which is no longer causing problems. Could the open header be screwing with the primary 02 heating up? Once warm the car pulls like a son of a bitch....

 

I was having a similar problem. Once its warmed up it idles fine right? If so its probably just your Engine coolant temperature sensor.

 

Yep, once its warmed up its fine.

 

Any other opinions?

 

Does the motor have a fitv?

 

No sir.

 

i have the same exact problem, on cold start it won't stay on so i have to stay on the gas for a good few seconds. Once it warms up it idles at about 5-600 rpm. I played with the rpm adjuster inside the throttle body but it does no good.