Rich idle after 10 to 15 seconds at 14.7

[Shanobi]

Hi Guys,

I wonder if anyone can help me understand what’s happening with my Air/Fuel mixtures about 12 seconds after reaching idle. Since fitting a new (R33 gtst) AFM the car reaches idle fine with the AFR at 14.7 ish, then after 10 to 15 seconds the mixture goes rich, to about 13.8. When the 02 flag is un-checked the ratio sits in the right zone and doesn't move, its only when o2 is on that the ratio turns rich. My best guess is some long term trims are causing the problem but I don't know how, why, or what to do about it

There's a 3” induction pipe between the MAF and turbo which directs the BOV straight into the turbo. The injector delay is the same as stock, mostly because the injectors haven't changed yet. The base fuel pressure is up a bit at 40psi. The o2 signal is simulated from a permanently installed innovate LC-1. I tried the AFM change tool for then injector multiplier but testing seemed to show a higher number was required at about 26950. (The attached config was when the logs were recorded, but changing the values hasn't helped)

Something else that confuses me is needing to set richer values at hight loads to maintain a constant AFR. Might that indicate that I've got the injector multiplier wrong?


180SX SR20 94'
Bosch 044
turbosmart FPR800
stock injectors
tomei pon cams
s14 turbo 14psi
font mount
r33 gtst AFM
3 inch inlet and exhaust

Any advise appreciated,

[Shanobi]

Here are some logs, just the interesting bit

[JaisEdelmann]

I have the same symptoms on my SR20DET Redtop.

Idles around 14.7 then after 10-15 seconds its goes to about 13.3. I have new fuel pump, injectors and MAF. I had the issue before changing any hardware.

I'm emulating narrowband signal to the ECU (narrowband is reporting rich at 13.3 so the O2 is telling the ecu its going rich).

Is there a correction table i'm missing? Is it possible to disable closed loop in idle? (if so how? - sorry i have not read the entire manual yet for nistune, so the answer is probaly there )

[Matt]

If you disable the narrowband, does the problem go away? Have a look at your fuel trim gauges to see if there is any change when you have the issue

You can disable O2 flags in the fuel map using the 'O' key (if the mixture is richer than 14.7:1)

There are other parameters for O2 sensing I still need to look into

[danielp11]

i have some experience from this from using narrowband simulation on my p11 turbo. The stock calibration for the innovate narrowband input is slightly different out the box from the voltage output of the standard nissan narrowband sensor. this causes the ecu to try and target a richer closed loop afr as it is sensing that the voltage is within the range it is looking for but in reality the innovate is outputting the right voltage but at the wrong afr point. using the innovate lm programmer you can adjust the voltage output of the narrowband signal to match that of the stock nissan oxygen sensor which if i remember right is 0v =15 afr and 1v =14 afr. this should bring your closed loop operation to 14.7.


p.s also be sure to clear the self learn on nistune before first startup after reprogramming the innovate to clear any fuel trimming from the previous innovate settings.
hope this helps

daniel

[Matt]

Some ECUs also provide the voltage levels which you can adjust in the Nistune software (not all ECUs however have this)

[UNISA JECS]

I've experienced the same exact things with OBDI ECU in the B13 and S13, the only way I can get it to stay at stoich indefinitely was by disabling the o2 sensor so I ended up not liking that and swtich to an OBDII ECU but would like to find a fix for the OBDI ECU, this only happens on a completely bone stock OBDI B13 S13 ECU by the way not just because of Nistune.

viewtopic.php?f=11&t=2773

[Matt]

Have you tried an OBD-I ECU using feature pack (keeping the ECU running within stock TP load scales)

Adjusting K constant to stay within existing TP scales (offset fueling with Total Injection Multipler parameter) seems to resolve most issues related to O2 feedback

[UNISA JECS]

Have you tried an OBD-I ECU using feature pack (keeping the ECU running within stock TP load scales)

Adjusting K constant to stay within existing TP scales (offset fueling with Total Injection Multipler parameter) seems to resolve most issues related to O2 feedback

I've done everything but that, but it's a problem even on a bone stock OBDI B13 SR20DE and S13 KA24DE regardless of chipped ECU has been my findings.

[bubblegum]

Bump.

Same thing on my type x 180sx.

Blacktop sr20det
Fmic
Walbro 255
Nistune
S15 injectors
R33s2 afm
264 hfm cams
S15bb turbo
98 always
Nismo fpr set to 42

Im looking for a setting to fix this or something. Ill try some of the already posted possible solutions.

My k and latency are all sweet. Just about 10 seconds ish my afr goes to 13.3...

Only really concerned cause it runs nice and lumpy at my 14.7 idle and smooths out at the 13.3 lol

[UNISA JECS]

I just learned to chalk this up as a OBDI thing, even the stock unmolested ECU will exhibit the same mannerisms, only OBDII controls the idle to 14.7 much much better but it would be nice if this can be solved but since it does it even with a stock ECU I doubt it.

[sr20truck]

Thought Id' chime in on this too, let me know if I'm off base here.

Have a stock sr20det rebuilt, all things proper, 26 mpg in the convertible 240sx on 4.09 gears, idles 14.7, then goes to 13.7 and sits unless you jab the gas quick on off fashion and then goes back to 14.7 Hook up nistune and watch idle behavior in fts and ftl areas, fts skyrockets to 21% while ftl sits at 0% every time. check fuel pressure, 50psi because no fpr, wahlbro overpowers factory regulator well known fact, ordered a nismo type a fpr, hopes to increase mpg, eliminate lean pops upon decel and occasional stalls by setting it properly. I imagine its also going rich at idle because of other factors like common elimination of all smog equipment and possibility that the 300zx tt o2 sensor may not be a 100% fit for our motors which is common as well. Furethermore a greddy full auto turbo timer that acts up once in a while is a sure sign that you have a grounding problem at the battery commonly relocated to trunk. voltage plays a big role in engine behavior which is why hks circle earth kit or equivalent is a proven item. ie I know someone with an awful engine bay harness tuck and he just cant idle at anything but 12.9, yet drives ok but not real good, which is obvious to say that nistune reports 11.8 volts while his new alternator puts out a perfect 14.2 at idle. stubborn.

[Lok]

I am also having this issue. 63 ECU with the FP update.

At idle the FTS is 0% and the FTL is -4% when the AFR is at ~13.0

I have also put the car back completely stock and used a stock ECU (no nistune board) and this problem still persist. The OBD 1 vs 2 might just be the difference.

If you rev the car, the AFR will stay at 14.7 for 10 sec then go back to 13.0.

I have disabled the O2 feedback in the 4 cells that it uses when idling with no improvement. The O2 sensor voltage is reading ~1.02-1.05 volts when its running the 13.0, so the ECU should know that its running rich.

Has anyone else had any luck on resolving this?

Are the J type ECU's OBD2?

[Matt]

Yes I see the same issue on my S14A SR20DET... its a factory ECU issue from what you guys have described and not sure on a 'fix'

The O2 sensor is swinging for about 10 seconds and adjusting injection after returning to idle to adjust the AFRs. Ideally it should be going back to about 14.7:1 but I am seeing it go richer. Tweaking the O2 rich/lean voltages in one idea I have but that will throw out the trims, other idea was changing the TP min table to see if I can combat it that way

[sr20truck]

I want to revisit this and clear up what my findings are. Idle short trim at operating temp will 0 out on a factory setup for example, then rise to 28% on the lean side, which pushes the wideband to 13.8 We aren't OBD2 with the s13 redtop and blacktop so this may not be addressable. I did play around with many tables with no success to correct this. Yet, upon warmup conditions, it does stay at 14.7 at idle in an almost fully warm condition. It may lead to an answer after looking into it further.