Test an O2 sensor - JeepForum.com

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post #1 of 22 Old 04-11-2011, 05:55 PM Thread Starter
scifone
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Test an O2 sensor

How do you test an O2 sensor to make sure it's functioning properly? I'm getting about 11mpg and I'm going through everything that could be causing this bad of mileage to try and eliminate it. I've already done cap, rotor, plugs, wires, fuel filter and air filter. I'm going to pull off my throttle body and clean that out as well as all the sensors.

Any other suggestions on improving my mpg will be greatly appreciated! I'm not expecting 20+ but I would like to get back to around 14 or so.

Thanks!

Robby

Edit:

Also I do have a small exhaust leak in the manifold and I have a replacement on the way.

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post #2 of 22 Old 04-11-2011, 06:17 PM
Nibbley15
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When I replaced my intake/exhaust gasket, and welded my cracked manifold my MPG went up a bit. I haven't taken an exact measurement, but before driving back and forth to work prior to fixing I was almost empty after 2 weeks, this time I'm still over 3/4 tank.
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post #3 of 22 Old 04-11-2011, 06:32 PM
JOExFROMxNY
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From the 1994 Wrangler / Cherokee FSM. see if these help:
Attached Thumbnails
02 sensor info from 1994 factory service manual_1.jpg   02 sensor info from 1994 factory service manual_2.jpg   02 sensor info from 1994 factory service manual_3.jpg  
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post #4 of 22 Old 04-12-2011, 05:48 AM Thread Starter
scifone
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Quote:
Originally Posted by Nibbley15 View Post
When I replaced my intake/exhaust gasket, and welded my cracked manifold my MPG went up a bit. I haven't taken an exact measurement, but before driving back and forth to work prior to fixing I was almost empty after 2 weeks, this time I'm still over 3/4 tank.
That seems like a huge improvement. My leak isn't horrible or anything but I can certainly tell it's there. I hope to see an improvement like that.

Quote:
Originally Posted by JOExFROMxNY View Post
From the 1994 Wrangler / Cherokee FSM. see if these help:
Thanks! That's a huge help. If I am going to replace the O2 sensor what brand would you guys recommend?
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post #5 of 22 Old 04-12-2011, 06:34 AM
oldtime_ironman
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Quote:
Originally Posted by scifone View Post
That seems like a huge improvement. My leak isn't horrible or anything but I can certainly tell it's there. I hope to see an improvement like that.

Thanks! That's a huge help. If I am going to replace the O2 sensor what brand would you guys recommend?
I prefer NAPA or Bosch (if available). FWIW the O2 sensor is pretty easy to remember: You should roughly see between 3/10 of a volt (300mV) and about 8/10 of a volt (800mV) on the sense wire depending on warm-up and running conditions. It should vary over time with temperature, throttle opening, etc. All measured to a ground point or batt negative. Only one wire is a sense wire; the other wires are for the heater that is built into the sensor, so don't be fooled.
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post #6 of 22 Old 04-12-2011, 07:16 AM
Que89YJ
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Scifone, do you work for Sprint? Its likely the O2 sensor, the cheaper generics work ok too, you just have to swap the electrical connectors on them.
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post #7 of 22 Old 04-12-2011, 08:11 AM Thread Starter
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Quote:
Originally Posted by oldtime_ironman View Post
I prefer NAPA or Bosch (if available). FWIW the O2 sensor is pretty easy to remember: You should roughly see between 3/10 of a volt (300mV) and about 8/10 of a volt (800mV) on the sense wire depending on warm-up and running conditions. It should vary over time with temperature, throttle opening, etc. All measured to a ground point or batt negative. Only one wire is a sense wire; the other wires are for the heater that is built into the sensor, so don't be fooled.
Thanks! That's very helpful. I'll test it out later today.

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Originally Posted by Que89YJ View Post
Scifone, do you work for Sprint? Its likely the O2 sensor, the cheaper generics work ok too, you just have to swap the electrical connectors on them.
No, I am actually still in college. Why do you ask? I definitely like cheaper. Thanks.
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post #8 of 22 Old 04-12-2011, 08:34 AM
Que89YJ
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I had a friend that just took a job with Sprint in KC. They moved in somewhere around you in Lawrence. Scifone sounded like a knock on sciphone.
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post #9 of 22 Old 04-12-2011, 08:43 AM Thread Starter
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Haha got ya. Sorry man. Thanks for the input though.
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post #10 of 22 Old 04-12-2011, 10:26 AM
Nibbley15
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Quote:
Originally Posted by scifone View Post
That seems like a huge improvement. My leak isn't horrible or anything but I can certainly tell it's there. I hope to see an improvement like that.



Thanks! That's a huge help. If I am going to replace the O2 sensor what brand would you guys recommend?
I wasn't expecting that much of an improvement either, but efficiency is efficiency.
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post #11 of 22 Old 04-12-2011, 03:03 PM Thread Starter
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Originally Posted by Nibbley15 View Post
I wasn't expecting that much of an improvement either, but efficiency is efficiency.
I hope I get that kind of improvement. I should be getting a new manifold from 1A Auto this afternoon. I'll report back with my findings.
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post #12 of 22 Old 04-12-2011, 03:20 PM
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I changed my exhaust manifold on Sunday and so far, the only improvement besides the sound quality is increased throttle response at higher RPM and from a dead stop. I havent had enough time to see any improvement in gas mileage, but since I got this one APN Header our findings would be different anyways. Oh and be prepared with an angle grinder to get that manifold to fit properly. I had to grind off 1/8th of an inch from the outside of both sides of every intake port in order to get it to slide onto the head dowels.
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post #13 of 22 Old 04-12-2011, 05:17 PM Thread Starter
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Originally Posted by thebeast64 View Post
I changed my exhaust manifold on Sunday and so far, the only improvement besides the sound quality is increased throttle response at higher RPM and from a dead stop. I havent had enough time to see any improvement in gas mileage, but since I got this one APN Header our findings would be different anyways. Oh and be prepared with an angle grinder to get that manifold to fit properly. I had to grind off 1/8th of an inch from the outside of both sides of every intake port in order to get it to slide onto the head dowels.
You had to grind the header in the link you provided or the one that 1A Auto sells?
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post #14 of 22 Old 04-12-2011, 05:31 PM
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I got my exhaust manifold from 1aauto and had no issues installing it. You can find my write up on it in the write ups section.
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post #15 of 22 Old 04-12-2011, 05:50 PM Thread Starter
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Originally Posted by Sleuthhound View Post
I got my exhaust manifold from 1aauto and had no issues installing it. You can find my write up on it in the write ups section.
I've read through your writeup more than a couple times. Good work!
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