02 Sensor/Lean Condition

[XiKeiyaZI]

So, it appears that my brand new 02 sensor may be dead. This morning on my way to work, the Thermostat housing gasket gave out and the car got a little warm (Halfway up the flag-like emblem). At lunch, I changed the thermostat and gasket with a brand new one. Suddenly when I went to drive home, I noticed the car was running very lean. I killed it, started it again, and it was running in the 12's, so I drove it home. No overheating, however!

Anywho, I immediately did a leakdown and compression test - all good. Compression shows above 163 across the board. I popped link in and gave it a look and found that my 02 is sitting, with thee key on, over 1.5V. I don't believe this is normal. When the car is running, the volts will slow drop, however, my Fuel trims will raise and I'll idle above 19afr. Every so often, the volts will rocket up over 2v's and then drop back down. I assume that this means the sensor is dead? Now, the wiring to the 02 sensor are connected using butt-connectors and solder, and they were taped up neatly (so I thought). I'm wondering if the super hot coolant may have somehow gotten to the wiring and possibly fried the 02 sensor?

Is there anything else I should immediately look at? Before today my idle and cruising AFR's have been 14.7-15.3, no more and no less. Today this happens and all of a sudden my 02 starts acting this way.

Also, is it possible for me to simply have my wideband simulate my narrowband from it's placement at the rear 02 position? There are zero exhaust leaks - I've made sure of this extensively. I just don't know how well the delay will play out, nor how I need to setup my pin assignments. Also, to do this would I need to sever the wiring between the front 02 sensor and the harness?

Thanks for any input.

 

[eclipse9504]

How long ago did you replace the sensor?

 

[XiKeiyaZI]

About 2 weeks ago.

 

[snowborder714]

I'm wondering if the super hot coolant may have somehow gotten to the wiring and possibly fried the 02 sensor?

This was my first thought. I would look into it before your sensor ground gets blown in the ECU.

I'm not sure how well the rear mounted o2 would work for sim. My guess is the delay might cause an issue, but I don't know if I've ever seen someone do this for actual data to provide.

 

[XiKeiyaZI]

So would you pull the ecu at this point?

 

[XiKeiyaZI]

Well, you know me Brian - I got an anxiety thing going and pulled the ECU. In the process of doing it I found that the old soldering point for when it was up front running on narrowband had weakened. I doubt this would cause a spike in Volts, however.

ECU looks just like the day you sent it to me. Not a spec of the tell-tale sign of damage anywhere. No fish smell. Looks good. I'll assume I'm safe there.

Now, as I don't feel like dropping $40 on yet another sensor, I'm going to return to Narrowband Simulation for a bit if I can't find an immediate cause of voltage spike in the sensor. Assuming I move my Wideband back up front, do I need to rewire it to the front 02 pin at the ECU or can I leave it feeding into the rear pin and simply assign that pin?

 

[snowborder714]

You can just simply assign that pin.

Make sure to unplug the front o2 as soon as possible to prevent any further damage to the ECU. Fried o2 sensors burn out the sensor ground pretty darn quickly. It's not a hard/expensive fix, but an inconvenience.

 

[XiKeiyaZI]

Roger that. Looks like it's time to get dirty, yet again.

 

[XiKeiyaZI]

Issue resolved. I moved my wideband up front, rewired it yet used the rear 02 pin as it's inlet, assigned the pins in Link, fired it up - viola. Switching perfectly and idles 14.4-15.1. Thank God for Narrowband Simulation.