Nistune Forums

hey whats going on Matt, guys? here is my really weird problem, my car, 84t with an 88na ecu, decided to cycle between stoich and extremely rich afr. from ~14.5 to ~9s. now, the bizarre part is that this isnt from second to second, or minute to minute, this happens, from what i have noticed, depending on my fuel quantity. i could go 30 miles at a good afr and the next 20 in the 9s. any ideas???

Im suffering from the SAME problem for the past.... damn... LONG time!
I will have a PERFECT tune, and then right when I drive everything will go down the shitter for a good 20 miles (MID 9 AFRS!) and then all of a sudden it will change and I will have PERFECT AFR's!

Im still battleing this issue, but have figured out that if I set "bit 3" off in the feedback switch on Nistune, it will stop doing this!

I haven't figured it out 100% yet, but will soon!
Good to hear someone else having the same problem!

ok, its not just me then? i thought this was the weirdest shit. when i drove from california to texas, about 1800 miles, i would fill up the tank and for the first 1/4 i would often get more than 100 miles, and right after that i would get 30 for the next 1/4. and it just kept doing that until the tank was empty. at first i thought i was a problem with the tank quantity sender, but then i noticed the pattern followed the afr cycling. i will take the "bit 3'' and turn it to off if its not there and see what happens. thnx...

alex

well, bit 3 turned off didnt do anything. still rich like a pig.

Ok now try setting "o2 feedback temperature" to 205 temp.

Burn it and try again.

i couldnt find where to set the temperature, what i did do was to change the k value from 215 to 155, which for 550cc injectors seems a little low to me. anyways, this brought the afr back to normal. what im afraid of is that this problem fixes itself and then i will be extremely lean until i change it again.

Matt, where are you........

I'm here... I dont know the cause of your problem yet. Is this something other Z31 guys have seen at all?

I know one of the problems was O2 feedback voltage was reading lean and making it run rich once O2 feedback voltage reached but this is a different problem so I would need to look into it further. Got any logs?

you guys need to check what your

(a) O2 voltage feedback temp is set to currently (stock)
(b) and if your O2 sensor is knackered - monitor this on the consult log window and it should be bouncing

if at any time when you are experiencing the issues, and can get a log of it, have a look at that signal. if it starts staying below/around 0.3 volts then the ECU thinks its going lean in closed loop and will keep adding more fuel until its pouring out the exhaust!

if your O2 sensor is knackered, then set the temp to maximum (yes 205 is the most) and see if it still happens. Bit 3 (0x08) is the o2 feedback switch bit which bypasses checking o2 altogether on Z31. Setting this will disable the o2 feedback

If you are still having issues after this, take a log of it with your AFR feedback included from the wideband and post it here. We can monitor everything and see what the conditions are for your AFRs to go crazy (leaner when cells should be richer)

the other thing is that if you are entering another cell which should be richer, but then your O2 feedback flags arent used in that region then it could go from rich closed loop to lean open loop conditions. enable the feedback flag settings and see if its in this area.

VERY useful information Matt!!!
I will try today and see if I can get this thing going.
Thanks!

thanx guys, *almost* everything is great now. just got to work on light load/low rpm cells now. these are off by more than 1 point still.