Can a bad oxygen sensor cause fouled plugs? - Page 2 -
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post #16 of 18 Old 12-19-2013, 12:28 AM
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Originally Posted by ShadowTek View Post
So if the purpose of the upstream sensor is to determine the "correct" air/fuel ratio, then the downstream sensor will force a different AFR to get the desired emmisions effect?

What happens if you unplug the downstream sensors? Can the upstream sensors not control the poper AFR without the downstream sensors?

This just seems like needless complexity.
The upstream O2 sensors control the AFR, the downstream ones are only there to detect a faulty cat, if you disconnect them it will throw a code.

The first thing I would do is swap both upstream sensors over to see if the problem moves to the other bank. If it does then your O2 sensor is faulty.

Without proper diagnostic equipment you have to use a process of elimination, not guesswork.

One thing at a time


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post #17 of 18 Old 12-19-2013, 04:35 AM Thread Starter
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I'm waiting for a cheap OBD2 scanner that I found on Amazon, so maybe that can tell me something. I've seen the Youtube videos where some scanners can display live voltage readings of the sensors and whatnot, but I don't know if the one I ordered can do all that or not.
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post #18 of 18 Old 10-10-2016, 08:49 PM Thread Starter
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Update: This thread was when I changed my plugs at 148k, and today I've changed them again at 183k. All the plugs have a consistent tan coloration this time, so I'll assume that the original issue was from the previously faulty o2 sensor.

Either that or my Jeep is self-healing with age.
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