Grounds are critical to these sensors telling you the truth.

All ground locations are not created equal so if the mfg instructions say ground to a specific location, just do it. If the ground potential for the controller is different than the sensor you get a ground differential and a false reading.

Just to verify, zero leaks upstream of the sensor ie header flange gaskets and no pan evac?

Kevin

This is great Info I am having the same problem woth my fast xfi system and mostly at idle.

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Here is an interesting check of the O2...
http://www.yellowbullet.com/forum/showthread.php?t=1275090

You shouldn't put too much stock in AFR readings at idle, especially with a lumpy cam. You set it so the engine is happy and the AFR is what it is.

With a cam with a lot of overlap you get a lot of random misfires or half fires at idle and all the oxygen that doesn't get used parades past the O2 sensor and you get a lean reading when in fact it could be/likely is pig rich.

Kevin

Somewhat related. Anyone using WRO2 in conjunction with crankcase evac?

How close can the evac lines get to the sensor before it may effect readings?

i know you need to have the o2 sensor up stream from the evac.

10 or 2 o clock
No leaks up stream

Yep thats the recommended . i had mine at 9 oclock.

on a straight pipe 9/3, never on the inside of a curve section..

A couple of inches is plenty as long as the O2
is up stream.. I have been a little closer without
any issue.. big overlap cams pulse a lot at idle

It's downstream, but I was worried about pulses. I got it sorted last night. Getting close to firing the EFI up if it would stop snowing...