edbacca

My stft seem to be in normal range, but there are two different ones that are further down in between the o2 readings one is stft b1 S2 at 99 steady and another stft b2 s2 at 99 steady. What do these mean? Is it fuel effiecincy?

JimFX4

The O2 sensors should not be steady- they should move quicly between .1 and .9. The O2 reads the stochiometric reading of the exhaust gas and either increases fuel or decreases it depending on the readings. A reading of 14.7-1 is ideal -which is around .5 volts from the O2 readining.

edbacca

Full read out
Fuel sys cl
Fuel system 2 na
Cal load. 22.7
Ect. 151
Stft b1 .8 to -1.6
Ltft b1. .8 steady
Stft b2. 3.1 to 0.0
Ltft b2. -.8 steady
Eng rpm 635 - 643
Spark adv 15.0
Iat. 75
Maf .7
Tps 15.7
O2 sb1s1 .72-.095
Stft b1s1 -2.3-0.0
Stft b1s2. 99.2
O2sb2s1. .09-.68
Stft b2s1. 1.6- -1.0
O2sb2s2. .62
Stft b2s2. 99.2
Fp vac 39.8
Command evap 32.5
Evapvp -.279
Baro 28.0
Cat te ii. 757
Cat te 21. 757
Ecu volts 14.5
Load 14.5
Eq ratio. .99
Reltps 2.7

edbacca

im a little concerned about the following stft b1s2 and the stft b2s2 should they be bwtween .1 and .9?
O2 sb1s1 .72-.095
Stft b1s1 -2.3-0.0
Stft b1s2. 99.2
O2sb2s1. .09-.68
Stft b2s1. 1.6- -1.0
O2sb2s2. .62
Stft b2s2. 99.2

edbacca

anyone have ideas?

edbacca

bumping up my thread still need help

kevhead75

stft and ltft are your fuel trims. Long term and short term. Your long term fuel trims will remain somewhat steady.

edbacca

ok after doing some research the following should not be reading at 99.2 percent,
Stft b1s2. 99.2
Stft b2s2. 99.2

unless im miss reading information, according to PID that is too lean, but i did read that the numbers could be at 99 until the cat and evap run through their drive cycle to give an accurate reading. could this be true? i have not gotten any codes showing that im running lean, just 6 misfire.

the cat and evap are still blinking on my scanner which means they have not completed yet. again this is all knowledge that i might be reading wrong. have really just started doing my own work on fuel injected engines.

kevhead75

Fuel trims are always trying to adjust to 0. Not sure the software you are using but that could be read as .8 which is close to zero. stft are important but usually what you want to monitor is your long term fuel trims. Short term is changing constantly to get the long term close to zero (stoichiometric 14.7:1)

norcal

Has anyone come to a conclusion as to why the S2 is stuck at 99.2 and the CAT and EVAP have not concluded their drive cycle.
I'm having the same issue.
Thanks
Tony.