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post #1 of (permalink) Old 03-14-2001, 09:21 AM
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Oxygen Sensor Voltage

I've really geeked out now. I've spliced into my oxygen sensor wire and ran it into a multimeter to understand how my stock engine/computer is managing my A/F mixture. I'm doing this because my new catalytic converter and muffler seem to be getting way too hot. The floorboard behind my driver's seat is too hot to keep my hand on it after a 20-30 minute drive. Even with a heat shield over the cat.

My questions are (1) Has anyone else looked at their O2 sensor voltages? (2) Or is anyone knowledgeable on the typical readings during on-road driving?

It seems that after everything is warmed up, I consistently run ~0.7V to ~0.75V going down the road. This is indicative of a rich condition, and may explain the overheating exhaust parts.

Any ideas to bring this back to the "normal" 0.4-0.6V range? I've looked at the 258 primer. It only mentions that the sensor may be bad, and I know from the changing voltage that it is functional.

And while I appreciate the advice to go to fuel injection, at this point, I don't have the money. So if anyone has any ideas, I'd like to hear them.

<font color=red>1986 CJ-7, 258, T-5, TR-TFI, Stock
</font color=red>
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post #2 of (permalink) Old 03-14-2001, 10:42 AM
Way Outta Control
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Re: Oxygen Sensor Voltage

If the 02 sensor is within normal voltage limits, rich to lean, and the voltage varies, chances are it's good.

Have you looked at the vacuum, or the timing to see if the engine is off timed?

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post #3 of (permalink) Old 03-14-2001, 10:59 AM
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Re: Oxygen Sensor Voltage


Thanks for the reply. I've seen the sensor voltage vary between ~0.3V to ~0.8V.

My vacuum at idle is ~20 in. Hg. and "stable", and I've set the timing to right at spec (9 deg. at 1600RPM, no vac advance, and no 4" or 10" lines hooked up) and rechecked.

<font color=red>1986 CJ-7, 258, T-5, TR-TFI, Stock
</font color=red>
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