I think I'll only be able to hold out hope of someone in the area knowing how to tune these cars and possibly do a street tune on it instead...Since the tune took place in 2016 and by a prior owner, I doubt I'll get a break. I use to live over in Lake Oswego, so I would no doubt take the car to them if I could, but I am in N. Idaho now.

edit
The IACV I installed is a Wells brand AC4157 it was priced about the same as it is for an OEM one, I called them and they didnt have much info on it other than it was made in Japan. So I assumed it was probably a re packaged oem IACV. I thought at first it worked, but after the car getting up to normal operating temperatures, it is still doing the same thing by dipping below 500rpms and wanting to die when coming to a stop; while the car is coasting from neutral. I am not sure if I need an "actual" oem IACV from STMTuned or MapPerformance. But this Wells IACV made no difference at all versus the OEM IACV. It looks identical to the one sold on STMTuned.

 

I've swapped IACVs, map sensor, plugs, coil packs, did boost leak tests, different springs and preloads on BOV, verified fuel pressure, and tried different injectors. Finally after completely retuning on new injectors the problem went away, it was incredible to be able to come to a stop like a normal person for once. However, the new (used) injectors were trash at cruising RPMs, so we put the old ones back in and adjusted the new tune for them, the stalling problem did not come back even on the old injectors.

summary: retune fixed it, but I think there are multiple factors that lead to this problem. The above list may play a part in troubleshooting, but I also think a poor battery or alternator can play a role in contributing to these problems, so I'm assuming sooner or later the stalling will come back. If it does, first things I'll do is have injectors cleaned and replace the battery and check all the grounds and boost leaks.

Sorry this is the same list of things you've seen everywhere else, but it seems like even experienced shops are also stumped by this issue.

 

I appreciate the information. I will also look into the injectors as a factor. I was told the car had 1200cc FIC injectors but they do not look like the ones from the website or sold on English Racing's website. Perhaps someone can ID them.


update 5/22

As previously stated, I installed that Wells AC4157 IACV yesterday, and with little surprise it made no difference, however a couple things I noticed today driving it. I read a few threads where people were having issues with stalling while the A/C was on, but in my case when the A/C is on and the idle hesitation/dip occurs when coming to a junction or stopping while the car is in neutral, it seems to somewhat not hesitate nearly as badly but still dips below 500 but with the A/C on versus it off it seems the hesitation is less severe. If the A/C is not on it hesitates worse and its much more obnoxious.

What I am trying next is a new "but used" OEM IACV off ebay, it looks identical to the original one that came out of the car (no exterior visible spring showing) I will try it and see...

I also came across an old thread that perhaps might be worthwhile. And kind of what I am thinking of because the car is tuned now and it has say a bigger cam in it, the IACV might need to be tuned for it?

This thread is from 2010, but another person had a similar issue that sounded like mine anyways, someone was ,mentioning "tuning" the IACV stepper motor with ecoscan or MUT

https://www.evolutionm.net/forums/ev...-question.html

I should also mention, on cold start, and when the car doesn't do the hesitation problem, the idle rpms is about 1000-1100 which does seem high. There was a ton of slack in the throttle cable bracket so I adjusted it some but it made no difference.


ID these injectors?

 

Those look like all the old low impedance injectors, my PTE 1200s look just like that, minus the stickers.

My retune is holding up, I can drive like normal now. That's after a year of stalling in traffic and rolling into intersections with no power brakes or power steering. The scary thing is that the original tune was fine, then this problem started happening out of nowhere. I wonder if I'll ever find out if it was a mechanical or electrical issue.

 

Dont know if you figured it out or not yet but I just had a similar issue with an 8 I just bought. Try relearning the idle. If the battery was disconnected and you get on the accelerator right after reconnecting it I guess it screws up the idle. Disconnect the battery for like 15 seconds reconnect it and start the car up put on all your accessories, heater, lights, etc and let it idle for like 10-15 minutes.DONT TOUCH THE ACCELERATOR at all. Once the time has elapsed turn the car off for a half a minute and after that it might fix the problem. Worked for me