Recently my aem eugo has been reporting very strange numbers after the use of some c16. Now, I know that leaded gas has ill effects on o2 sensors. But my question is how can I tell if the o2 sensor is faulty?

Here is a couple logs from my pocklogger this morning:

The first one is during car start up...

RPM/o2 1 Bank 1/o2 Trim 1 Bank 1

1145/0.6/14.84
1152/0.58/15.63
1137/0.6/13.28
1145/0.56/13.28
1125/0.54/13.28
1113/0.58/14.84
1125/0.54/14.84
1113/0.58/15.63
1125/0.56/16.41

This log is a quick drive down my road...

RPM/o2 Bank 1/o2 Trim Bank 1

1082/0.5/7.81
1051/0.7/9.38
1484/0.56/7.03
1297/0.64/7.03
1270/0.62/4.69
1609/0.62/1.56
2102/0.66/-2.34
2473/0.64/-7.03
2555/0.1/-6.25
1926/0.3/-1.56
2027/0.54/3.13

My aem during these two logs was displaying an a/f in the range from 11.2-13.8.

I believe that I have a bad o2 sensor, but I need some help/advise in reading these logs to see what is normal/abnormal. These values for the o2 seem high as they are normally in the .02 range when not wot.

I have alot more information on the logs so if you need more info just let me know and I can post it up.

Thanks guys!

 

maybe what I am looking for is a better understanding of the o2 values of the stock o2 sensor and how the numbers correspond to either being lean or rich?

Is there a way you can estimate what the o2 value will be by converting it from the narrow band oem o2 sensor, to a wideband output?

 

Not sure on your logs, but it only takes about 3 gal of c16 to kill an O2 sensor, especially the Bosch.

 

during wot the o2 reads fine, .96 as the ecu is in open loop. But just during idle and normal driving the o2 jumps all around, and is never close to 14.7...like it used to be

 

Hmm, I see you are talking about an AEM with bosch sensor.

Usually they fail when they cannot read richer than 13.00.

 

My aem eugo jumps around during normal driving and idle conditions, which isnt supposed to. Normally when crusing say at 3000rpm in 5th gear the a/f on the aem (wideband) would read 14.7 constatly until the load/tps changed.

I understand the operation of narrowbands, but for some reason my aem eugo is not reporting 14.7 at these conditions. Which itused to just a couple of days ago.

Thus, leading me to believe that something is wrong with one of the sensors...

 

That's how my readout is! I'm running a Bosch through a plx r-500. I think it's just noise in the system. In my case, it's always been doing that and my best guess is that it's probably dude to running the signal wires through the same firewall hole as the wiring for the trunk battery relocation.

 

Let me clarify my setup.

I am using the stock ecu with a flash with the oem o2 in the o2 housing.

I then have a seperate aem eugo wideband in the downpipe...

2 seperate o2's

 

Thats interesting. I have never had a problem with this except for recently after the use of c16.

Under wot everything seems normal in the logs, but during cruising conditions the a/f seems weird. When I start the car cold, or warm, the a/f which is being reported back from the aem could read anywhere from 11.9-13.8..

So either the aem sensor is bad and is not reporting back the right a/f, or the front sensor is bad and the o2 is sending voltage to the ecu making it think it is running lean so it is dumping in fuel. Then the aem is reporting back the rich condition that the car is running due to the faulty front o2...

Does this sound right?

 

The aem reports back conditions richer than 13.00 so I am assuming that this o2 is not the culprit...

 

I did find some useful information while searching to find a way to test the stock front o2 sensor...

http://www.mr2.com/TEXT/O2_Sensor.html

 

Mine jumps around a little when im just driving around or idling, i think the culprit would be the front sensor in the o2 housing, ever since i started running lots of leaded fuel my AFR's jump around when not at WOT. My friends evo does that exact same thing....he thinks its the front o2 as well.

 

/\ thats good information.

Once I got out of school I got the car into open loop mode and held the rpms at 2500-3000 for a steady minute or so while watching the voltage on the pocketlogger for the front o2 and the aem wideband.

This is supposed to be a test to see if the o2 is bad or not (one of several ways)

Once I let off the gas, the afrs went back to normal during idle and crusing speeds~14.0-14.9. They hardly ever went into the 13's.

I will continue to watch it and see what it does and compile more logs, but as of right now it seems like it is back to normal...

I am going to check for vaccume leaks (again), clean the mafs, and change back my boost source on my mbc (this is the last thing I did before I had this issue) and see what happens. If none of those seem to work, then I will swap the mafs and see if that does the trick.

I will report back with my findings.

Hopefully this information will help others who have the similar problem down the road...

 

I thought I would just replace the front o2 sensor since it has a 1 year warrenty anyway...

After removing the o2 sensor, it was completly white/light grey...got lead?

So, I replaced the sensor and the car is back to normal, absolutly perfect!

Just thought I would post this information for others who might have the same problem.

Sparatic o2's which show on a wideband, is most likely a bad o2 sensor.

 

Update for me as well. I put electric tape around all the wires going through the firewall and it seems to have fixed the problem. No more "noise" but by the sound of it the readings don't seem to be right. When I let off the gas, boscho reads 19.9 which is full air which I think makes sense (since no gas is going through the exhaust) but you sayd you get 13-14? Are my readings wrong?