I have a d16y8 in my 99EX. It was obd2b and it ran absolutely flawless.

I'm setting the car up for turbo. I got the conversion harness and it's now running a p28 (no CEL). Since then, the cold idle is around 2500rpm and it surges, then it idles OK at 750 or so when warmed up. Right now, the only change I have made is with the ECU.

I thought OBD2 motors do not have a FITV? I do have something under the throttle body with coolant lines going to it. I was expecting the idle to be too low, not too high. I tried unplugging the IACV on a cold start and it ran perfect, so I know it's the IACV making these changes.

I didn't want to mention this, but the ECU is chipped and I'm running crome which I am tuning myself. I have tried so many different adjustments with advanced idle control, ECT vs idle, IAT vs idle, advanced tables, IAC compensation, etc... nothing changes the cold idle. This cold 2500RPM surging idle is driving me nuts!

Any ideas or possible tricks?

 

I heard Crome has this problem with surging idle. I have it too. Didn't have it before I boosted it and it's not just cold. Sometimes it will idle just fine and otehr times I get the surging. When I get a chunk of change I'm switching to Hondata as it's my understanding that Crome is no longer being developed and hasn't been for a while.
http://www.turbod16.com/viewtopic.php?f=12&t=42913

 

Thanks for the response. I believe you are right. You can always tell when a motor is running on crome. But I believe there are always special tweaks you can do to fix things.

I made it alot better by making several changes. In the advanced tables, I changed the ignition battery offset and the ECT vs idle speed (lowered the lower temp and raised the higher temp). The surging is gone but it still runs at 2500 and slowly decreases as it warms up. I also pulled a little timing and quite a bit of fuel in the idle range. Hopefully I will get better mileage

One thing people rarely notice in crome is that the factory idle is set for 750, but in the advanced tables in ECT or IAT vs idle speed, its listed at 650 when warmed up. If these numbers don't match they will fight each other and can cause a surge. Also, people will change the target idle without modifying the other tables. There is also the advanced idle plugin for further tweaking. Maybe this will help you?

 

It would if I knew how to tune. If I get into it before I go Hondata I'll keep this in mind.

 

I don't think that a 2500 rpm cold idle speed is out of the ordinary when the weather is cold.

I will also copy this thread to the Engine Management forum.