Fluctuating/hunting closed loop with no load, idle perfect

[Furble]

Hi, my first forum post, hopefully I get this right.

To be more specific the problem does not exist in idle, nor does it noticeably exist (unless I look for it) when the car is under load. It is very noticeable if you attempt to hold down the accelerator pedal steady at any rpm over idle when in neutral or when free-revving. Maybe that's normal, I just feel like I would have noticed that before with my old motor (which was d16z6) or with any other Honda I've ever driven.

So when attempting to hold an rpm in closed loop in neutral the revs go up and down and the AFRs cycle from 13:1 to 15.5. I believe the cycling mixture is what is raising and lowering the rpms.

I've been having the problem for a long time. I've ruled out all mechanical possibilities. I did my swap about a year ago and when I first did the swap everything was bone stock EXCEPT CAI & Headers on my b18c1 OBD1. That said the problem existed on the stock setup with the original ECU that was original to the motor and a brand new OEM O2 sensor. I knew I was going to do a bunch of upgrades back then so I figured/hoped one of those upgrades would fix the problem. Since then I've changed everything (new manifold, new gaskets (now using Hondata heat shield), injectors, regulator, throttle body, new new new you name it, every part on this car is either new OEM or new aftermarket).

I also since switched the stock O2 for a PLX wideband. This not only replaced the O2 (which was a new stock one anyway) but also replaced the wiring for the O2. Now it goes direct from the sensor to the PLX box and from there direct to the ECU which was originally stock but is now Hondata. All wiring used was high quality GXL rated pure copper wire.

I thought maybe the stock O2 was slow or something, or maybe the wiring was making it slow, proven not the case by changing sensor and wiring.

The wideband is grounded directly to the thermostat housing.

Car runs great/spot on in open loop. Was tuned by a professional tuner with a great reputation.

Attached are the calibration and a log clearly showing the issue.

I find I can improve it a lot to the point where it's almost negligible playing with the short term trim settings, most notably the settings for Rate of Change. This makes sense but I can't help feel like this is not normal. Maybe it is? Again the problem doesn't exist at idle and not really under load either. Just if I rev at neutral.

If anyone can validate if this is normal or not or come up with a brighter idea that would be awesome!

[Spunkster]

According to the calibration you are running in open loop.

If the issue is in closed loop, then you will have to play with the closed loop settings for rate of change and the min and max amount of adjustment it allows. You will also have to look at long and short term fuel trims.

[TTR]

Try this. I use these settings with an AEM X series and work really good. These settings work good with the oem sensor so try it with a stock sensor as well if you want. The base values for rate of change do not work well imo.

[Furble]

Thanks guys, that helped, got it sorted!