PDA

View Full Version : what do you guys make of these O2 sensor logs



audispeed
02-27-2006, 08:54 PM
first off, sorry for the poor resolution, pulls had to be done in second gear because anything faster is impossible on the DC area highways except at 3 in the morning. I am hunting the cause of my car running lean. I thought it was the O2 sensors, so I logged their output voltage. Tell me what you guys make of this. Also, at idle, the O2 sensors constantly wobble from .1 volts to .8 volts very frequently, maybee once every second or two. Do you think these O2 sensors are bad? To me it looks like they are telling the ECU that the car is running rich when it definitely isn't. Anyone agree? If so time to put in the new O2 sensors.

wierd thing is, my idle fuel trim is at +3%, but my @part fuel trim is at -16% and I know that the car is running lean. in both cases.

Thanks for any help.

data is from the same run, jsut on two different plots:


http://www.vu.union.edu/~archibad/pics/audi/2-27-06%20copy.jpg

http://www.vu.union.edu/~archibad/pics/audi/2-27-06-2%20copy.jpg

k0mpresd
02-27-2006, 08:58 PM
.8 is about 11.75 a/f ...not lean @ all

logs look ok

edit: boucning @ idle is normal..the ecu is constantly making adjustments and thats just how narrowband sensors work @ idle and partial throttle...thats why narrowband a/f gauges are constantly bouncing back and forth @ idle/partial throttle

audispeed
02-27-2006, 09:02 PM
Originally posted by k0mpresd
.8 lambda is about 11.75 a/f ...not lean @ all

logs look ok

is voltage the same as lambda? Because those logs are the O2 sensor voltage and the voltage only goes from 0-1, so I dont see how it would even register lean that way. I was reading somewhere that .55 and up was rich for an O2 sensor.

audispeed
02-27-2006, 09:03 PM
Originally posted by k0mpresd
.8 lambda is about 11.75 a/f ...not lean @ all

logs look ok

edit: boucning @ idle is normal..the ecu is constantly making adjustments and thats just how narrowband sensors work @ idle and partial throttle...thats why narrowband a/f gauges are constantly bouncing back and forth @ idle/partial throttle

jsut thought of this, if the O2 snesors are reading rich, that solves my problem. The wideband on the dyno told me that I was running lean and the fact that the ECU is pulling 16% of the fuel verifys that.

k0mpresd
02-27-2006, 09:04 PM
if it was 0 it would be really lean

.55 and up is on the richer side of things...but you want the car to be atleast @ .8v @ wot

.8 is not too rich under boost..if it was less than that id be concerned

k0mpresd
02-27-2006, 09:05 PM
you really have to take the tailpipe sniffers w/ a grain of salt

they tend to read a little leaner than what the actual a/f is

audispeed
02-27-2006, 09:07 PM
Originally posted by k0mpresd
if it was 0 it would be really lean

.55 and up is on the richer side of things...but you want the car to be atleast @ .8v @ wot

.8 is not too rich under boost..if it was less than that id be concerned

thanks for the help. The dyno was showing my A/F around 14-15 undre boost and 16-17 at idle. So my theory is that if the O2 sensors are telling the ECU the car is running rich and then pulling fuel, that would explain my lean condition.

k0mpresd
02-27-2006, 09:08 PM
you still have a cat and resonator?

audispeed
02-27-2006, 09:08 PM
Originally posted by k0mpresd
you really have to take the tailpipe sniffers w/ a grain of salt

they tend to read a little leaner than what the actual a/f is

I completely agree, but the other supercharged cars were running much richer then mine and my LTFT is pulling 16% of the fuel on both banks. This kind of confirms the problem.

audispeed
02-27-2006, 09:08 PM
Originally posted by k0mpresd
you still have a cat and resonator?


yeah, so did the other supercharged cars

k0mpresd
02-27-2006, 09:11 PM
w/ those logs though i still wouldnt be concerned

get yourself a wideband for in the car monitoring..that would be my only other suggestion

audispeed
02-27-2006, 09:13 PM
Originally posted by k0mpresd
w/ those logs though i still wouldnt be concerned

get yourself a wideband for in the car monitoring..that would be my only other suggestion

i have a wideband that I will hopefully get around to installing this weekend. My theory is that the O2 sensors are falsely reading a rich condition when the car is actually running lean. They have 110k on them and probably could use a replacement anyway.

k0mpresd
02-27-2006, 09:16 PM
nice about the wideband [:)]

i see what youre saying though..its really hard to tell since all the info doesnt really match..your o2's versus the dyno and the fuel trims...

audispeed
02-27-2006, 09:18 PM
Originally posted by k0mpresd
nice about the wideband [:)]

i see what youre saying though..its really hard to tell since all the info doesnt really match..your o2's versus the dyno and the fuel trims...

yeah, i know. I figure I might as well replace them. I may replace 1 and see if there is any difference in the readings or LTFT values. That way I will know if they are a problem or not.

Thanks again for the help.

Now I just need to stop being lazy and get the damn wideband in.

k0mpresd
02-27-2006, 09:20 PM
if you want me to check prices on the o2 sensors PM me

i can check on them tomorrow @ work

i dont know if ill be able to beat ecs's price though

k0mpresd
02-27-2006, 09:21 PM
what kind of wideband did you end up going with?

audispeed
02-27-2006, 09:23 PM
i ended up going with the zeitronix. thanks for the offer on the O2 sensors, but I just got some in a couple days ago from ECS. Hopefully I will have time to install them tomorrow and we will see if that solves the problem.

k0mpresd
02-27-2006, 09:24 PM
oh nice..zeitronix looks like good stuff

keep us updated on whats going on w/ the car ..and make sure to remember to reset the ecu after you replace those o2's

audispeed
02-27-2006, 09:28 PM
will do. thanks.

xcdhracer15
02-28-2006, 08:07 AM
it would be better if you had a log of 02 sensor and like block 001 so you could put rpm in.


time slots wouldnt be exact but only like .2 seconds off.



if you do this send them to me and i'll make and a/f graph for you over the rpm range. go from 3-6500 rpms. in 3rd gear or if you can 4th gear

Daft
02-28-2006, 08:46 AM
I really wouldn't base your true A/F off of the stock O2 sensors. They just aren't made for this type of reading. They are ballpark readings at best.

You can see a .8v reading and assume it is still good but, that .8v is a vague reading. It's really for the ECU to get a sense of how to adjust the mixture in close loop operation (part throttle).

Open loop operation under WOT is going to result in solid values but, once again, they are approximate at best.

If you really need to keep an eye on A/F, a wideband setup and an EGT gauge will give a good view of what's coming out of the motor.

audispeed
02-28-2006, 09:18 AM
Originally posted by Daft
I really wouldn't base your true A/F off of the stock O2 sensors. They just aren't made for this type of reading. They are ballpark readings at best.

You can see a .8v reading and assume it is still good but, that .8v is a vague reading. It's really for the ECU to get a sense of how to adjust the mixture in close loop operation (part throttle).

Open loop operation under WOT is going to result in solid values but, once again, they are approximate at best.

If you really need to keep an eye on A/F, a wideband setup and an EGT gauge will give a good view of what's coming out of the motor.

Daft - I have a wideband that I am installing this weekend. the concern arose out of the fact that the car was running lean at the dyno. this, combined with the fact that the O2 sensors are indicating a rich condition, leads me to believe the O2 sensors may be the cause of teh lean condition. considering that the ecu is pulling 16% of the fuel out on both banks, it seems that the O2 sensors may indeed be the problem.