I have a UEGO wideband installed into my evo and for the most part it works fine. However, there are times that the car will be idling and it will go from the stoich 14.7 ish that it idles at to full lean. The car will still run fine as far as the idle goes, and when I start moving it goes back to normal. Just wanted to know if anyone else has experienced this sort of problem, any feedback is appreciated.

 

Also, the car was doing this for a while and my buddy borred it and killed the battery by leaving the lights on. After he jumped it, the problem went away. A week later it started doing it again so i checked the battery, which is the original battery, and it had no water in it at all. I filled the battery up with distilled water and the problem went away. Which leads me to believe that the problem is with the battery, so I'm going to change to a optima battery and go from there. Also, its worth noting that the car is somewhat finicky, some days it will run bettter than others. For example, if I log the car one day it will be fine, the next it will knock, sometimes kinda bad. I'm switching the battery out today, any other suggestions are appreciated. Thanks!

 

Mine would be all over the place while at idle as well.
At WOT, it was steady.

I would like to know if that was normal behavior as well.

 

Yeah mine is the same way, it is steady at WOT but even cruising at 3-3.5K rpm it still reads all the way lean. I just got a new battery and put it in, and at first it was fixed, but within 20 min or so its back to how it was. It really only reads if I am at more than 50% throttle, and every now and then when I am idling, if for a long enough period of time, it will go back to reading correctly. The car never changes though, always runs the same so I think it has to do with the gauge.

 

At idle the computer is always correcting itself. So just like the like the narrow band light show gauge it sweeps back and forth between lean and rich. When at wot it should read steady.

 

Well what I meant was that at idle it was reading all the way lean and the UEGO wasn't even registering a number it just has the three dashes. Also I have the apex'i turbo timer wired into the regular narrow band O2 sensor and it reads full rich at the same time that the wideband is reading full lean, so on the turbo timer its readying 10.0'1/ 4.99. At idle the turbo timer will read something like 15.8-1, while the wideband is reading full lean. Im confused. Just to clarify, its not ocilating back and fourth at all its either reading fine, or not at all, If i put my foot in it, its fine and it reads fine at WOT, but anything less than half throttle and nothing.

 

Well, i lied, it does sweep back and fourth but only from 14.6-15.3, but this is only when it is running right and actually registering the way that it is supposed to.

 

i had this exact same problem which I incorrectly attributed to aftermarket cams. check for an exhaust leak. that was my problem.

 

where is the sensor mounted?

 

the sensor is mounted into a bung that in the test pipe, I'll check for an exhaust leak, I'm putting in a helix SS 02 sensor housing so I'll just do it then, but I do know that both joints of the test pipe and the rest downstream are welded together.

 

What would be the best way to check for an exhaust leak?

 

Is your UEGO the gauge type? I purchased one but read about quite a few issues similar to yours and calibration problems, so I sold it and bought an AEM standalone uego controller instead. That has been working perfectly for me.

 

Yeah its the gauge type

 

My UEGO (gauge type) does the same thing at idle--I've got cams in an MR. However, at wot, it holds at 14.7 with very slight fluctuation +/- .2.

At idle, often times the car will idle so low that the guage buries itself on the lean side and won't register anything unless I blip the throttle to bring the rpms back up.

 

idk, alot of this doesnt sound right. i.e.; Sounds like exhaust leak, calibration issue or sensor is bad, but i guess it could be the gauge too, but more likely to be one of the above issues, from the sound of it...?