View Single Post
Old 03-22-2006, 08:24 PM   #8
JoBoo
Scooby Specialist
 
Member#: 23423
Join Date: Aug 2002
Chapter/Region: NESIC
Location: slummahvul,ma www.comscc.org
Vehicle:
05 STi / 08 Dmax
IDP Racing Tech Monkey

Default

I cant tell you for sure what the symptoms mean without knowing the circutry in your car.

In the wrx, only the front O2 gives feed back to the ecu on fuel and maybe timing. the rear O2 is strictly for emissions. if your getting a cel for too rich/lean, then either its working and you are running rich or lean, or the O2 has gotten "lazy" which is also common. Lazy = alive, but not reading properly.. maybe due to soot, deposits, damage, or just plain age... from the chart it looks like the first one is reading something, but the second one is not. From the graph, I dont know which is front or rear...

Best thing to do is check the wiring diagram for your car, and see what things are supposed to do, then test things one by one... process of elimination is the best course. key is understanding what the proper behavior is.

do a search on the web... this is an age old problem since the introduction of O2 sensors.. theres lots of info on types, proper behavior and ways to diagnose the problems...

edit:
from what I know, most late model O2's switch back and forth between a "high" voltage, and "low" voltage. for example high can be >0.7v and low can be <0.2v the actual voltages vary by sensor type. the reason they fluctuate is because of the exhaust valve timing you get pulses of gas not a continous stream. so in those pulses you have instantaneously rich and lean gas passing by the sensor. it should read that fast and see that. if not it can give you a faulty reading = lazy...
* Registered users of the site do not see these ads.
JoBoo is offline   Reply With Quote