So I had my car tuned a few months ago, and was sent a video file of my idle at 14.9 or so. Spot on. I even checked the ROM and it shows it should be right around there. The issue is this: Ever since I got the car back, it does NOT idle at 14.9, it actually goes so lean that my AEM gauge displays -- (over 18), or at the very least will display 17, 18, etc. This only seems to happen at idle, and under load AFR seems fine (at WOT, and mostly partial throttle as well).

The kicker is this: when the car FIRST starts up, for the first 10-15 seconds, it does show 14.9 or so, and the RPM is around 15-1800, then just goes lean, and idle drops to around 12/1300. During this time, it feels like it wants to stall out, and the only thing keeping it from doing so is the fact that the IDLE has been raised to 12/1300 or so.
Another kicker: When I turn on the AC, if the idle was acting erratic before, the same thing happens. Within the first 10-15 seconds or so, IDLE AFR will actually go to 14.9 or so, and then after about 15 seconds or so, goes back to lean. It's odd that when under load, it temporarily fixes the issue.

Tuner has not responded to messages for over a month, so I am tackling this issue on my own now.
I honestly can't think of where to start looking. If I had to take a guess, it sounds like a fueling issue, but I can't find anything wrong other than a semi loud Wally 255, but I hear that is normal for these pumps. A boost leak test was run at the tuner, as well as compression and leak down.

What would be a good direction to head for this issue?

MODS:
Running E85, previously on 93 only.
Full 3" exhaust from turboback
Stock Turbo
Tial 50 BOV
Tomei PonCam Type R - 270/270
Wally 255
FIC 1100 Injector
3" SD intake
Speed Density tuned
EGR and Emissions delete.

 

You don't have a fuel system issue if WOT AFR's are the same.

It's either the tune, or a wonky front O2 sensors. You need to log the O2 feedback and long term fuel trims.

 

I sure hope it's not the tune, as the tuner is a pretty well respected and highly rated tuner on these forums/ in the Evo world. I won't discount it, but I sure hope that's not the issue. I will be able to log some things later today or this week, but is there something specific I am looking for with the o2 feedback? Specific voltage or just that it recognizes it?
Same question with the LTFT? Anything specific I should be looking for to signal an issue? Thank you or the response as well!

 

You're looking for them to be maxed out at at 25%, or reading zero (indicating they're turned off)

Judging by your difficulty in reaching him I'm going to guess it's TSComp. Being well known and respected and doesn't prevent one from making errors or having the occasional issue.

 

That is true! I will do some logging in the next day or so and post back! Thanks for the starting point!

 

I purposely run my roms with a lean idle. Turning off closed loop at certain loads. As others have said, log the data and check it out.

 

So it's not so much that I mind the lean idle, as I don't think it's really hurting anything. It's more that the car feels like it wants to die, and the idle will fluctuate from time to time as a result when not under load. It's very annoying, and makes the car often want to stutter under low loads (like when going under 10MPH).

I should also add that when doing things like going down a hill, when off the throttle but still in gear, it also goes lean. This does not seem to happen when cruising on a flat surface in gear, even if I take my foot off the gas.
Will log when able to and report back! Thanks guys

 

SO I ran some logs and it appears, from the logs, that my O2 Sensor is bad. The voltage is very low as can be seen from the photo. I will be replacing that hopefully this weekend. Hoping it makes some difference.

 

It sounds like to me that the heater circuit in the O2 might be the culprit. If it were me, I would put my inductive amp-meter on the heater wires (on the sensor) and check the current draw. If the heater does not warm up it will have high resistance and cause these symptoms. Since you do not have the problem under load it sounds like the hot combustion gasses are heating up the sensor lowering the resistance causing it to work correctly. When it cools down- the resistance goes up causing your symptoms to return.

just my 2 cents

 

O2 sensor would make sense and was my first guess while reading your post. Usually problems in closed loop only = sensor.
all cars go full lean during decel. That's normal.