Need your thoughts about the Oxygen sensor - JeepForum.com
 
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post #1 of 11 Old 08-20-2017, 09:25 AM Thread Starter
dodgemahally
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Need your thoughts about the Oxygen sensor

Before I bought my 95 4.0 ZJ it sat in a driveway for 7 years straight and before that it was pulled behind an RV for most of its life. As a result, being a Michigan Jeep, it is rust eaten, but the interior is like new.

On to my question: would you replace the O2 sensor as a matter of maintenance? Or, test it with a DMM for resistance value and leave it alone if it is within the spec published in the FSM? Another consideration is that my ZJ seems to run good, but maybe it would run better if I replaced it. I get 19-20 mpg.

Next, what brand sensor is most recommended by you folks? I have used Rock Auto for years but lately they seem to really be dropping the ball. For example, every O2 sensor they list is designated upstream or downstream....correct me if I'm wrong but isn't there only one? Recently I bought a ujoint for a front wheel that was way to small and was told by an aficionado here that that size was never used on a 95 ZJ. (Sorry to rant on RA)

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post #2 of 11 Old 08-20-2017, 11:42 AM
jayxtee1
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O2 sensors aren't hard or expensive to replace. In my opinion, it certainly couldn't hurt. I have a 96 ZJ and there are two sensors that are both pretty easy to get to and change with just a wrench.
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post #3 of 11 Old 08-20-2017, 12:49 PM
Uniblurb
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You're correct dodgemahally your 95 4.0 only has one o2 sensor which is upstream on the downpipe. OBD1 93-95 only has one where the OBD2 96-98 with more electronics/emissions has the additional downstream/cat o2 sensor.

The OE brand of o2 sensor is NTK and below is the NTK 23119 upstream for your 95 4.0 which is $33 plus shipping on Rockauto.

http://www.rockauto.com/en/moreinfo....182103&jsn=391

Some say the Mopar o2 sensor made by NTK may have a different spec than the just normal ones made by NTK. But I've never had problems with the non-Mopar NTK o2 sensors on my 96 4.0.

Your mileage at 19-20 mpg sure is good and not sure if a new o2 sensor may change that or cause it to drop lower? Upstream o2 sensors have a lot to do with fuel trims and seems like yours must still be working. Your choice whether to change it out or not and good luck.

PS. If you do decide to change it out it's best to spray a bunch of rust cutter ahead of time on the base of the o2 sensor where it does into the bung (threaded part) of the downpipe. Then let it run and cool down some while removing it with exhaust warm. A 6-point o2 sensor socket is often recommended so you don't round off the nut shaped edges. Sometimes if they're really rusted or seized in there they can be a bear to remove.

96 4.0 ZJ Laredo, 2004 4.7L WJ Limited, 96 4.0 XJ (son's)


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post #4 of 11 Old 08-20-2017, 12:51 PM Thread Starter
dodgemahally
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Quote:
Originally Posted by jayxtee1 View Post
O2 sensors aren't hard or expensive to replace. In my opinion, it certainly couldn't hurt. I have a 96 ZJ and there are two sensors that are both pretty easy to get to and change with just a wrench.

Okay, what brand did you use? I have heard that some brands are not calibrated correctly(In this case a Jeep 4.0)
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post #5 of 11 Old 08-20-2017, 12:58 PM Thread Starter
dodgemahally
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Thanks Uni.......great info, as always and very thorough. You the man!! Unless you are a lady, which I doubt very much. Ha!

I'll leave it in, for now.
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post #6 of 11 Old 08-20-2017, 01:02 PM
Uniblurb
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Think we were posting at the same time, lol, and read my above post.

Below is a member with bad o2 sensor on his 95 4.0 where he was getting a code and only 13-14 mpg. And he didn't have much fun in changing it out in his last post.

http://www.jeepforum.com/forum/f13/4...-51-a-4080849/

Edit/addition: just saw where you read my post and you're welcome. Thanks, and I am pretty wordy! Lol.

96 4.0 ZJ Laredo, 2004 4.7L WJ Limited, 96 4.0 XJ (son's)


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post #7 of 11 Old 08-21-2017, 01:50 PM
jayxtee1
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Quote:
Originally Posted by dodgemahally
Okay, what brand did you use? I have heard that some brands are not calibrated correctly(In this case a Jeep 4.0)
I believe I went with Bosche. I actually found them for half the price on Amazon, and had AutoZone price match them while I was in the store. Running much better ever since. Then again, one of my wires was completely in two... ha!
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post #8 of 11 Old 08-21-2017, 03:11 PM
Uniblurb
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Quote:
Originally Posted by jayxtee1 View Post
I believe I went with Bosche. I actually found them for half the price on Amazon, and had AutoZone price match them while I was in the store. Running much better ever since. Then again, one of my wires was completely in two... ha!
Actually there's been quite a few on here who have had compatibility issues with the Bosch o2 sensors in these ZJ's. While it may be running better than broken wire o2 sensors sometime you may want to look at your fuel trims with a scanner.

As mentioned before NTK are the OE o2 sensors and it may run even better with a new upstream NTK sensor for your 96 4.0 like mine.

96 4.0 ZJ Laredo, 2004 4.7L WJ Limited, 96 4.0 XJ (son's)


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post #9 of 11 Old 08-22-2017, 08:26 AM
LouC
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I changed the upstream sensor on our '98 because it was doing the rough running after cold start thing which is a sign of a lazy upstream O2 sensor. Totally cured that and as a bonus it runs quite a bit smoother as well. I used an OE Mopar sensor; pricey but worth it.

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post #10 of 11 Old 08-23-2017, 08:45 PM Thread Starter
dodgemahally
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Quote:
Originally Posted by Uniblurb View Post
Actually there's been quite a few on here who have had compatibility issues with the Bosch o2 sensors in these ZJ's. While it may be running better than broken wire o2 sensors sometime you may want to look at your fuel trims with a scanner.

As mentioned before NTK are the OE o2 sensors and it may run even better with a new upstream NTK sensor for your 96 4.0 like mine.
You friggen nailed that one Uni!
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post #11 of 11 Old 08-23-2017, 08:50 PM Thread Starter
dodgemahally
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Quote:
Originally Posted by LouC View Post
I changed the upstream sensor on our '98 because it was doing the rough running after cold start thing which is a sign of a lazy upstream O2 sensor. Totally cured that and as a bonus it runs quite a bit smoother as well. I used an OE Mopar sensor; pricey but worth it.
Bingo-----nice catch dude. That was smart, and now your happy. Love an engine with good manners like yours. You inspired me to swap out mine. After I do some simple daigs with a Volt-ohm meter..Ha!
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