Bad 02 sensor??? (datalog info inside)

[Parsalian05]

i just got my datalogger working today (and im very VERY happy with it, i suggest everyone with a dsm get one ASAP), i did a few runs and checked out my o2 readings and timing. at first i didnt know the difference between 02 sensor 1 and 2, so i couldnt come to any conclusions as i was driving, really.

i did a log of just cruising around 30mph in 3rd gear with JUST my o2 1 being logged (the one closest to the turbo)... it was reading .08! i did some logs at WOT and at higher rpms at 15psi or so, i found my o2 1 sensor still read very very low (.23 was the absolute highest it got), but my o2 2 sensor was reading .94! also, in WOT, my timing was 12 or so... very retarded considering i was only running 15-16 psi on my evo3 16g(check my mod list, i should be running 17-18 just fine).

i know .5 is the ideal voltage and a bad o2 sensor will either read very high or very low, but im assuming it's my 1st o2 sensor that's going bad. i also know that the 2nd o2 is after the cat and isn't nearly as important and the 1st one. one other thing, lately, my gas mileage has been terrible and i backfire if i boost 16+ psi.... i just fixed 3 big boost leaks and that helped a bit.

does this sound like the classic bad o2 sensor diagnosis?

 

[Parsalian05]

another thing... if my ECU is getting very lean readings from the o2, it would overcompensate in fuel, making it rich, right? then why is my timing getting pulled so much and why am i backfiring at relatively low boost?

also ill add that, when all these mileage probs started, my idle also got a bit messed up and i had to turn the BISS screw to get it back up. even now, if the car is warmed up, my idle will be unusually low.

 

[Parsalian05]

can anyone please help me out? i dont wanna spend $100+ on a new o2 sensor if im not sure that's the problem . i know a bad o2 will result in bad gas mileage, but ive also heard that it messes up part-throttle driving, but it's my full-throttle driving that's hurting...

 

[AWDPetmitsu]

While idling, does the value of O2 sensor 1 fluctuate? If not, or if it fluctuates slowly, then it's dead. Also, how long has it been since it was last replaced? If it's been over 80,000 miles, you should change it anyway.

 

[Parsalian05]

it fluctuates very slowly between .05 and .08v. i just ordered a Bosche replacement from SBR, only $80 with shipping, unlike the Mitsu part, which is $120. ill post again to let people know if it was really a bad o2 (i hope it is).

 

[blackGSX2g]

Any news on that? I just replaced my front o2 sensor and it still idles at like .04-.08 volts. The sensor seems to work when I'm off the throttle coasting and at WOT, but not at a cruise. Sensor is brand new...any suggestions??

 

[blackGSX2g]

nobody?