Hondata

Hey everyone, I’m new here and still fairly new to tuning. Most of what I’ve learned so far has been through Jeff Evans’ Performance Academy. I’ve been chatting with Jeff on the academy forums, but I wanted to bring the issue here in case anyone else has some insight.

So, last year, I tuned the car in closed loop and it ran great. AFRs at idle were right around 14.5–15.0 with little to no trims, and overall drivability was solid. About a week ago, I decided to retune the car and dial in the idle and cruise in open loop. Upon switching to open loop, the AFRs went full rich on the gauge. If I lean it out to 14.7 in open loop, then the AFRs go full lean when any electrical load is applied.

Vehicle & Setup:
Turbo 99 Acura Integra GSR
P28 ECU with Hondata S300 v3 (via OBD2 to OBD1 jumper harness)
Walboro 255 fuel pump (relayed)
45psi base fuel pressure
FIC 1000cc injectors (dead times set per data sheet)
OmniPower 3-bar MAP sensor (selected in SManager and manually calibrated - scalar of 617 and an offset of 11)
AEM X series wideband (analog output white wire to D14, analog ground brown wire to A23 -PG1)

The Issue:
In closed loop, the car idles perfectly at 14.7:1 AFR with trims within ±1%.
switching to open loop, it immediately runs extremely rich (AFR ~8.0:1 at idle).
I have to pull 50–60% out of the fuel table just to get it back to 14.7:1 in open loop.
Also, in open loop, any electrical load (headlights, rad fan, power windows, etc.) causes idle dips, bogging, and full lean AFRs, which are not present at all in closed loop.

What I’ve Checked So Far:
Wideband is wired correctly: D14 for analog output, analog ground to A23 (ECU power ground). AFR on gauge matches what SManager sees.
MAP sensor seems accurate: reads -0.9 inHg at key-on, manually calibrated using OmniPower 3-bar data.
ELD is disabled under Parameters.
Fuel map has been rescaled for 1000cc injectors, deadtimes set per FIC's datasheet.
No excessive coolant or IAT fuel enrichment at operating temp.
Idle injector pulse width is 1.3ms with 1% duty cycle, which seems normal.
ECU voltage is stable around 13.9–14.1V at idle, no alternator dips.
And all grounds seem to be fine.

Why is the car perfect in closed loop, but massively rich in open loop? Is this normal? If not, Is there a hidden compensation setting I might be overlooking in SManager that only applies in open loop?

Any help or ideas would be greatly appreciated. Thanks in advance!
Steve

You shouldn't use D14 as it cannot see the full voltage range. Use D10 instead as it reads the correct range.

Spunkster wrote: Mon Jun 02, 2025 12:57 pm You shouldn't use D14 as it cannot see the full voltage range. Use D10 instead as it reads the correct range.

Thanks for the reply, I am aware that D14 can only read roughly 3.7v, but with the AEM wideband, that's roughly 16.2:1. And I don't plan on being in that range, ever. I am willing to switch to D10, if you think it could be causing my issues, but I don't see how it could.

You should try using the D10 input and see if that helps.

Alright, I'll switch to d10 and let you know.

So I switched to D10, and the AF was jumping back and forth from rich to lean. So I pulled the sensor out and did a free air calibration and the sensor failed. So this whole time I've been pulling my hair out, the sensor was on its way out. At least I'm hoping this is the issue.

Yesterday I was at least able to get it to idle at 14.7 in open loop, I just had issues with it going full lean when any electrical load was applied. My worry is that the issue will still be there and the sensor just went bad from me trying to diagnose the issue.

I got a new lsu4.9 ordered, so we'll see what happens.

A new bosch 4.9 sensor fixed my issues, You can go ahead and close/delete the thread. I feel like an idiot lol. Its been a great learning experience though. I never knew closed loop could mask a wide band issue. Now I know.