Nistune Forums

ok well here goes. i have a 91 SER with a sr20ve w/N1 cams that i cannot get to idle right when cold with the o2 sensor turned on. the car will idle when you turn it on for approx 15secs perfict after that the car jumps to 16-17 to 1 afr. now this happens only when the car is sub 80c. after the car is warmed up and you come to a idle the car will drop from 14.7 afr to 13.7-13.9 after 10 secs. i have tried messing with the k value playing with the inj latency and even the cold tables but none seem to help. now when i turn the o2 sensor off the car idles all day at 14.7 if i set the idle values to 192 or 0 and will start up in the low 13's and come up to 14.7 after about 15 secs no matter what temp.

May be it's Yours O2 sensor defected? And not giving good reading?

o2 sensor is brand new. i have tried 2 o2s with and same issue. the o2 sensor ossilates like its supposed to when driving. the thing that is wierd is when you come to a stop when its warm the o2 will change over .50-under .50 and then it settles at .85 ish and thats when the afr goes into the 13's. on a side note what is the lag time on the stock sr20ve inj?

ok more information today. the car starts up with .32v on the o2 pritty much no matter the temp. after the initial start up the o2 volts will drop to.00 or .01v and thats when the car runs lean on the wideband now this will stay with no voltage untill you raise the rpms over 1400 then it goes into the normal rich lean cycle. at a complete stop the voltage bounces and then comes to a halt at .85-.87v and i get a nice rich 13.7-14.0 afr. what the heck would cause the o2 to do this and what controll do we have over it?

O2 feedback kicks in at a certain temp. I see for B13 SR20DE its not defined yet... so I'll try and add that in

once the temp is reached, if below a 'lean' voltage then ECU will make richer and if below a 'rich' voltage then ECU will make leaner. causes that cycling that you see

once you are driving the O2 should be in closed loop mode and do this cycling but not when accelerating (should also do it when idling)

the o2 seems to work fine when driving in the closed loop area. its the idle area that seems to be out of wack. the car idles fine for 5-10 sec then the o2 seems to when the car is warm run to a high voltage .85 or so and if the car is cold it runs into .01v or so. there must be some thing in the ecu that is triggering this? maybe some sort of rpm trigger? i can get the cars afr to run fine with the o2 off but i would like to be able to use the o2 since up here we get 4 seasons and i dont want to have to retune the part throttle every few months.

Have you tried a coolant temp sensors. sounds like it could be a lazy one. Also on the sr20ve engine You have to make sure the throttle body mechanical lever is not working. If this is making changes with coolant temp you can have issues like this.

temp sensor is in spec with fsm data. the mechanical cold idle on the car works flawless. it seems to be more of a time thing in the nissan code. some sort of temp or time trigger for the o2 sensor. the reason i say that is due to the fact that no matter the temp of the engine the car will always start up with .32v from the o2 sensor and slowly rise. car runs great during this time if its cold or hot. after this the o2 sensor v will drop to almost 0 unless i am driving above idle rpm if the car is cold. when this happens the car hits 16. or so afr. if the car is warm and been driven the o2 sensor voltage will peg at .85v at a idle after a few seconds. then the car runs rich at 13.7-13.9 afr. now my old det did the same thing i just thought it was some thing to do with the large 760cc inj and s4 cams i was running in it.