Stock sensor values on idle

[Bee-RSkyline]

Trying to diagnose what seems like a rough/miss on idle.

Does anybody have a list of sensor values seen on idle?

When I reset the ecu, issue goes away for a while but randomly returns after a period of time.
Could be a couple lights, or a day or two.
Nistune board on modified rb20. No fault codes.

Only thing i see standing out is the TPS voltage on idle.
Idle switch is working.
Could a higher sensor voltage on idle cause the ECU to try and adjust to compensate?

[Skym]

Sensor voltages (MAF, o2 sensor) vary due to idle stabilisation. Same as idle rpm.

Miss on idle can be due to o2 sensor making ECU make engine go lean (lean missfire) or adjusting to intake airleak, intake manifold airleak, exhaust manifold leak, weak fuelpump, etc. Turning o2 sensor off via raising temp to max stops engine missing, but check A/F ratio via wideband afterwards, as could be adjusting to something making engine go lean.

Oil is too thick and engine struggles to idle. Use 5w40 or 10w40 oil and a good oilfilter.

MAF has an airleak behind it (stuttering, similar to failed coilpack). Could be crack in rubber intake piping between ribs, crack in rubber intake piping under intake hose clamps, etc

Sparkplug gaps are gapped too close or fouled (need to drive on motorway to clean them). Same with o2 sensor. Usually engine idles smooth after a 100-300km run.

[Bee-RSkyline]

engine was recently tuned w/ a wideband o2.
plugs cleaned and gapped.
no stuttering above idle.
Does the ECU need the stock o2 signal? is it safe to disconnect if running and aftermarket wideband?

[Skym]

Ran without o2 sensor on my car for while (unplugged it until I could replace it) and it didn't damage anything (but checked A/F ratio via wideband afterwards to make sure everything was ok). It was very smooth at idle.

From what I understand, ECU + o2 sensor adjust's A/F ratio below where knock maps would kick in on fuelmap. It's a safety feature (protect engine from blowing up due to running too lean) as well as a fuel economy feature. Factory have to make sure it last's the 3?year or 100,000km warrenty period. Some say if fuelmap is tuned correctly, can disable o2 sensor. I think as long as engine doesn't have any problems (mentioned in post above), it would be ok to disable it.

[steveo1502]

I swapped my turbos, guess I forgot to plug them in, 4 months with no 02 and didn't even know

[ToroGTS]

I'd check ignition system, particularly coil packs and ignition timing.

[Bee-RSkyline]

Splitfire coils less than 1000k , new plugs, swapped ignitor w/ no change.

When idling smooth timing reads back 15 degrees on idle
When it is rough time reads back 18 degrees in idle

Definitely seems as if the ECU is trying to compensate for something.

Gonna try unplugging the factory o2.

Thanks for all the input guys!

[Skym]

Could be faulty CAS, as it can change ignition timing by 1-2 degrees. But normally idle stabilisation on ECU can vary ignition timing (as seen via timing light) by roughly +5 or -5 (I think is supposed to be -4? degrees when look at idle stabilisation min and max tables via Nistune tuning software). I think idle stabilisation adjust's to o2 sensor making ECU make engine go rich, lean. Disabling o2 sensor should help stop ECU doing this.

[Bee-RSkyline]

I read through the logs and was definitely seeing a lean idle voltage.

Disabled the o2 sensor feedback loop via nistune and things are much more stable on idle