What are some causes of a false rich condition for my PCM o2 sensors. Both of them seem to think the car is rich, meaning they pull fuel till the a/f is in the 20.1 range or higher and the car is not drivable.

My wide band reads fine and the car runs great in open loop. I even put my wideband in one of the other o2 spots and it still read fine. Both of the pcm o2s are staying together number wise so its hard to beleive they are both bad, not to mention they are new.

 

What brand of O2's did you buy?

 

I tried a coupld GM ones I had around, and the others were aftermarket. Both read the same.

 

Have you checked the wiring to make sure you don't have the heater voltage leaking into the sensor wires? Are there any high voltage wires running close to and in parallel with the O2 sensor wires?

Based on your other post, both sensors are reading the same side of the exhaust, because you run both sides into a log, and then into the turbo. Probably would have been a good idea to post all the info here.

 

Yes, I forgot to mention. I have both sensors into a cross over pipe that goes from one manifold to the other. Therfore they are both reading the right bank.

Ill check on the wiring, one of the sensor wires runs pretty close to the starter. But wouldnt that only effect one of the sensors?

How would I check for heater voltage leaking?

 

It would show unusually high voltage, even with a cold sensor. When they are cold, key on, engine off, they should read about 450mV. If they are significantly higher than that, they are getting voltate from an outside source, not just the reference voltage from the PCM.

 

Checked the voltage. 453 to start with the car off, as they heat them selves up they drop, sounds normal to me.

Will an exhaust leak look like a rich, or a lean condition? I always thought they showed up as lean.

 

Exhaust leak in an NA setup will show up as a lean condition, which the PCM corrects by elevating the long term fuel corrections. With the added backpressure of a turbo system, I'm not sure if the exhaust gasses would still be educting air through a leak.

 

What really confuses me is that the wideband isnt picking up this rich condition.

 

Agreed that a datalog would help. That would help us understand if the issue is the O2 sensors themselves or the PCM's interpretation of the O2 sensor signals. I am learning towards the latter since the wideband doesn't match what the PCM thinks the narrowbands are saying, and the sensors have been replaced.

 

I will post a datamaster log or two when I get home.

One thing I noticed in the logs is that I am in cell 18 for 95% of the time it seems like.

 

Here is a .uni file for anyone to look at if they care. Thanks


http://home.comcast.net/~jared111481/sdbasecl.uni

 

I'm looking at frame 1398...

The O2 sensors are maxed out rich (977 mv). The PCM's L-Terms are bottomed out at 108, so it's at its limit of being able to remove fuel. It does look pig rich from the data here.

How much cam are you running? I have the LT4 HOT cam in my car and I ended up switching it to an open loop tune simply because it could not maintain a stable AFR at low engine speeds (below 2400) in closed loop. I'd see things like split L-terms, and overly rich conditions when the wideband shows its on the lean side. It runs better with an open-loop tune.

 

Im still runing my le1 cam. LE doesnt release exact specs, but its midd 220s/mid230s on a 110 LSA with lift close to .600

 

I'm thinking more along the lines of a bad wideband, best way is try putting the wideband into another car or run the car in open loop and see what the wideband says at start up. If your wideband said 20:1 and the o2's said perfect 14.7, thats an equivalent of almost 4 points, your car wouldn't run at 10:1 on the street, it would fall flat on its face and hesitate like crazy durring cruise.