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Old 01-21-2014, 11:03 PM   #1
BC_ZX3
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AEM wideband reading bounce

Not sure if it's a problem or not as car runs normally and performs as usual; my AEM wideband reading bounces around a bit too much for my liking (sweeps/oscillates from 13 to 16 very rapidly at part throttle cruise) although readings at full throttle and idle are generally steady and within spec.

Is this an indication that the wideband sensor in the exhaust is going belly up or of some other possible problem with the AEM unit (or engine)? Curious as to any one else's experience and possible cause and fix. Thanks.

Car's a turbocharged Zetec, no oil consumption, wideband is about 3 year's old.


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Old 01-21-2014, 11:16 PM   #2
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Mine does the same thing and is fine, oddly enough about the same amount of yours (3+yrs).

What I'm assuming is happening is the computer adjusting the air/fuel ratio to keep it within the targeted mark. Being that the computer uses a narrow band O2 to do this, this is why it bounces back and forth. It's just going back and forth since it can't read a actual reading.
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Old 01-22-2014, 08:33 AM   #3
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Its ment to go back and forth and the more you ease in or ease out of the throttle the more it changes , to hit the target of 14.7 it has to see it want past 14.7 to correct it and bring it back when it goes to low it sees it and brings it back up and so on

Its called Short Turm Fuel Trim 1 STFT1 and you can see this in your datalog watching the STFT1 , it should look like a castle top and should target 1.000 but never hit it

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Old 01-22-2014, 08:44 AM   #4
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Thanks for the responses.

I kinda knew it was supposed to oscillate a bit; it just seems to be more extreme lately. (Then again I'm doing more cold start, short trips.) I'll have to do a datalog as you suggest for peace of mind.

Just out of curiosity while we're on the subject, any idea what the life span of the AEM exhaust sensor really is? I see they sell them separately from the gauge kit. I assume it would be close to the same as a "regular" O2 sensor.
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Old 01-22-2014, 10:21 AM   #5
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Widebands do not last as long as narrowband o2 sensors. I believe they last about 15k miles.
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Old 01-22-2014, 01:16 PM   #6
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Quote:
Originally Posted by codices View Post
Widebands do not last as long as narrowband o2 sensors. I believe they last about 15k miles.
really? thats kinda shity
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Old 01-22-2014, 01:16 PM   #7
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They last quite a while. No shorter than any other sensor.
People replace then too often for the simple fact of safety and piece of mind. Unless you're logging response times and comparing them to older logs, you can't definitively say a sensor is going bad.
The downfall of having the sensor there doing nothing isn't as good as if it's running the car. Then you can do at will tests to see if it's slowing up.

In a nutshell, you compare PW to the WBO2 readings. They should match, peaks and valleys. 99% of the time they won't because the person didn't correct the 'offset'. And in those cases so long as the shaped of the graphs match, the sensor is fine.


Also, depending on how fast the gauge is reading, or able to datalog, the delta may not be real. You could be seeing individual exhaust pulses (rich) and dead time (lean). but I really doubt the gauge response is that fast.
But the tighter you are to 1, the better the tune. For instance, part throttle steady cruise I vary +/- 0.03 Lambda or 15.15 - 14.25. Lots of time into my tune though.
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