My AFR at cruise and idle is always 14.3 is this ok or is there a problem, I know it should ideally be at 14.7. Am i right in saying that when cruising or at idle it is purely the o2 sensor that is determining the amount of fuel and therefore could this be the problem my car is a evo8 which is pretty much stock except TBE and panel filter.

 

Stock they run rich but, I thought, only at WOT or open loop. It does seem a little rich for idle and cruise. Mine is at 14.9- 15.2 at idle and light cruise. Of course I have done quite a bit of mods to mine! have you done any retuning or changed anything in the ECU? What ROMID do you have? How many miles do you have?


Josh

 

Im on romid 93660005 and yes its tuned but nothing has been changed that would affect closed loop fueling.

 

Which Wideband are you using to measure?

Is it possible the wideband is reading incorrectly?

 

mine seems to fluxuate between 14.3-14.9

 

Its a innovate lc1 the wideband seems to be working fine (i suppose its difficult to actually tell) my fuel trims all look ok one thing i noticed from doing some logging at idle is the o2 sensor voltage generally fluctuates between 0.3v and 0.8v does this seem normal i thought it should be more around the 0.4-0.5v but i could be wrong.Im thinking that if the fuel trims are within tolerance and assuming my WB02 is correct the only thing it could be is the o2 sensor.

 

With the front o2 sensor is it simply a case of it either works or it does'nt? Or is it possibe for it to be off slightly?

 

i have the same wb...now im curious to see if mine is reading correctly or not..

 

In closed loop you are running solely off the front narrowband O2 sensor, nothing in the fuel maps at all. The sensor is designed to achieve an exact 14.7AFR target (1.0 lambda) and if you had an exhaust leak it would read leaner than it actually was. Its either an inaccurate stock 02 sensor or the WB is reading slightly off. When I'm running off the front O2 sensor, my Zeitronix WB reads exactly 14.7AFR when cruising on the highway at a constant speed and load.

 

Thats what i thought so assuming the WB02 is working properly does this mean that its almost definately my o2 sensor thats at fault?

 

when I was in closed loop I would get 14.3 to 14.5 readings with my lc-1.

either one of the sensors could be the culprit or the car is designed to run that way.

the point that many of the lc-1's read the same would, based on your prejudices, suggest something. I was inclined to trust it, but it doesn't really matter.

iow if the car runs fine, why worry.

 

heres a log of my a/f while just cruising around...seem about right to you guys?

 

I understand what your saying and youre probably right the car runs perfectly at 14.3 but i was just trying to figure out why when most people say it should be 14.7 do you think running ever so slightly richer will affect anything like mpg or plug fouling, a sensor here in the UK will cost me $130 im not sure whether its worth changing just to see if it will bring my AFR's up to 14.7 at idle and cruise.

 

The car is NOT designed to run that way! Its a standard 14.7/1.0 lambda O2 sensor. If they intended anything else they'd have a speficic sensor for a different target. Trust me, I've seen enough evo's cruise at the average 14.7 to confirm its the correct design.

 

Hey,i just installed my Lc-1 w/xd16 gauge,and at idle and cruise its showing 14.3 to 14.5.I just started scaling my maf for the intake i have and my ltft low is now .101%,and the stft bounces around + or - 2%.Im still getting the rich readings at idle.Is there anything that can lean the idle and cruise out?