So i installed a brand new AEM UEGO wideband about 2 months ago on my Evo9 MR. Since the day i installed it my AFR at idle always read 16-18, at the time i figured it was the tune and didnt pay much attention to it because of that and since it was only at idle and not WOT. This was on stock inj w/ walbro 255 and just a quick little reflash tune btw.

Fast forward today as im trying to get tuned by Tom aka TSCOMPUSA (whos been nothing but overly helpful on helping me diagnose the problem) i noticed that even on perfectly stoich fuel trims at idle, my wideband is still reading lean in the 16-18 range. Another sympton iv noticed is that now after installing the 1250cc inj when the car idles lean (like it always has since the wideband was put on) it now idles rough and is jerky sometimes part throttle. I know its not the tune since my trims are good and front o2 feedback is good aswell, so that leaves me to think that something is causing my wideband to show lean AFR (when its really not) which in return gives me rough idle while idling.

What do you guys think the problem could be? Boost leak, Exhaust leak, Vaccum leak, something fuel related? All help is appreciated, Thank

P.S. sorry for the long paragraphs lol

 

Bump for some advice? Need this issue resolved

 

Change the wideband, borrow another one and see if you get the same readings.

 

Yea im gonna try that aswell as the front o2 sensor and check exhaust leaks, my only question is would the wideband reading incorrectly lean cause the bad/rough idle and strong smell of fuel?

 

bump for some advice

 

where do you have the wideband position on the dp? how do you have it angled?

 

I have it where the stock rear o2 sensor was, do you mean angled with a defouler? If so then no its not angled

 

your wideband should be on the downpipe, if you have it in the rear of the exhaust where your 02 sensor was you're going to be reading super lean.

 

Damn maybe thats the problem then, and when you say on the DP do ypu mean on the o2 housing where the front sensor is or is there a bung on the dp?

 

LOL, not the 02 housing....there should be a bung on the downpipe, if not you need to get one welded.

 

Yea i just looked it up and noticed that thats where it should of been mounted, but iv seen people say that the rear o2 position is fine also? Would a few feet forward cause that much difference/bad idle?

 

the wideband itself won't give you a bad idle...but not running a rear 02 sensor when there should be one there could effect the idle unless they bypassed that in the ecu. i've been told by numerous of people the wideband should be on the downpipe closer to the exhaust manifold for better readings.

 

Yea i dont have the rear o2 patch delete because then the fuel trims arent able to log on evoscan. What afr should the car idle at? Btw my wb is wired to log from the ecu, idk if that has any effect on the actual car or tune tho?

 

14-15afr at idle is normal, if you have a rear 02 sensor put it back in and put the wideband on the dp bung. let us know what your afr is at idle. as far as the questions with your ecu contact TOM since he is tuning you.

 

So i switched out my front o2 sensor and WB sensor with a evo buddy of mine and the problems still there. He runs his WB sensor in the rear o2 sensor spot and has zero plroblems. What i did notice is when i pulled my wb sensor out it was completly black as if my car is running super rich yet my front o2 looked fine maybe slightly whiteish. Im clueless as to what the problem is now "/