02 sensors - Page 2 - JeepForum.com
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post #16 of 25 Old 07-07-2020, 05:26 PM
Johny Sawdust
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Bought a TJ with 150k. Put in a new motor and it was just not running quite right even with no codes.

Using my hptuner I noticed a lot of reads looked wrong. Two things can cause that-motor problems or the sensors giving the computer bad information. I started changing sensors and noticed the readings changed and the motor started running better. I am now in the camp of changing sensors regularly. Best guess is to do it about every 100k or when an issue related to sensor information makes the engine run funny. The computer will adjust engine parameters based on the sensor readings it gets so a sensor that is off even a little bit can make your engine run less than optimal.

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post #17 of 25 Old 07-07-2020, 06:05 PM
JoMc67
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A slight Thread Jack...I purchased 4 4.7 oxygen sensors ($100 each) thinking I needed all of them, but it turned out I only needed two near the converter.
So, I have two brand new 4.7 Mopar sensors left over (I guess these are called pre-cats sensors).

If anybody wants them $50 each, or &90 for the two.
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post #18 of 25 Old 07-08-2020, 07:57 AM
LordHobbit
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To ease removal, I've soaked the sensor a few days in (your favorite brand) penetrating oil. After a warm-up drive, I carefully crawl underneath with the exhaust still hot and carefully so as not to burn myself extract the sensor using my 02 sensor socket. The heat helps a great deal. But be very careful it is all hot. Thick leather gloves help in this situation.

I let the system cool before installing the new sensor.

However, on my Dakota I couldn't reach the sensor with any tools. So I left the old one in, cut a section of pipe out and welded in a new bung. The new sensor is in a place where I can easily reach it with my tools.

93 red ZJ 196k 4.0. Spent more money than I should have ...
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post #19 of 25 Old 07-08-2020, 11:34 AM
three_jeeps
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I replaced the 2 downstream sensors on my 2004 4.7L at ~75K and ~90K miles because they threw a code. One way is to change them when they fail. The other way is to change them ~80K (this varies depending what you read i've seen 60-100K). I prefer to change things on my own time. Given that you are at 130K, I'd replace all of them and be good for another 80+K miles.

You may get the old one out with a socket wrench if you cut the wire - but you are not going to get the new one in without damaging the wire and cutting& splicing is not recommended. Get the right tool for the right job - Since you are going to replace all the sensors at one time, you can buy/borrow the O2 tool than take it back....
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post #20 of 25 Old 07-13-2020, 07:03 PM Thread Starter
xjpete
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Just wanted to know-why not the Bosch 02 sensors? I know years ago on my Yamaha motorcycle, the Bosch spark plugs didn't work well at all. NGK was OEM spark plugs and really every other plug didn't work right. On the other hand I believe my 97 XJ uses the Bosch 02 sensors. they work fine in there.

2001 Jeep Grand Cherokee WJ Laredo 4.0 purchased Sept 2014.
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post #21 of 25 Old 07-13-2020, 11:23 PM
NWDC
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Quote:
Originally Posted by Uniblurb View Post
Interesting Waterluvr and thanks for the info.

The below info for oxygen sensors and exhausts from wjjeeps is incorrect for my Fed emissions 04 4.7. As already mentioned I have 2 upstream and 2 downstream oxygen sensors when it isn't CA emissions. Those 4 o2 sensors are before/after each small cat (2) under the engine and they're showing those small cats only for CA emissions.

http://wjjeeps.com/oxygen.htm

Plus my OE exhaust never had a cat in front of the muffler as shown in the below diagram for Fed emissions and there was just a large muffler.

I believe wjjeeps gets a lot of their info/diagrams from the FSM and official parts manuals. Jeep/Chrysler never was big on keeping their FSM's updated from year-to-year and most often just used the same info as the previous years.

The below diagram from wjjeeps is the exact same one in my 04 FSM (p.14-40) which wasn't ever updated showing 2 small cats on the Federal emissions 4.7. Oh well, what you physically see is what you get!

BTW, the torque spec for oxygen sensors is 22 ft.lbs in case anybody can squeeze a torque wrench up in there. I just tighten them until they feel right and use the copper non-seize on the threads if it comes with them.

Below is the diagram mentioned before from wjjeeps and from the 04 FSM (p.14-40) which isn't correct for my Fed emissions 04 4.7. Since xjpete who started this thread has the 01 4.0 I might as well throw in the image for oxygen sensor locations on the 4.0 too.
I have a 2000 4.7 with Federal Emissions (2 sensors), can you tell me the difference between the front and back sensors? Do both of them send data to the cpu affecting the engine or is it just the front sensor?

I'm looking to swap these out as preventative maintenance (168k), do you recommend spending more on Mopar sensors or is there other brands that you would recommend?
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post #22 of 25 Old 07-14-2020, 12:56 AM
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The downstream sensors work to monitor the health of the converters as well as to _protect_ the health of the converters. They can, and do affect fuel trim. I've seen people replace just the upstream sensors to resolve fuel economy issues and it turned out the downstream sensors were the culprits because they were countermanding the output of the upstream sensors.

So when you replace them definitely replace all of them. That said, the WJ sensors have exhibited very long lifespans, so if your check engine light is not on and you're not having fuel economy or closed loop performance issues then my suggestion is "if it ain't broke don't fix it"
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post #23 of 25 Old 07-14-2020, 09:19 AM Thread Starter
xjpete
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Kolak-last summer driving my Jeep fuel mileage read between 16.4 to 16.8 and on highways was better on a long trip overall. I had to sit in traffic for maybe 15 minutes of stop and go driving and mileage only dropped slightly. Rebuilt transmission, new coil rail and I'm still getting 15. 8 maybe on my 10 mile ride to work that is mostly non stop driving. The previous owner didn't even change the bald tires, the torn axle boot, and I seriously doubt the 02 sensors were even replaced. The 1st time it went in the shop to change the torn axle boot,the mechanic told me the spark plugs were all different brands so he changed them. I feel if you are an owner of a vehicle if you cant maintain it properly,you shouldn't own it. The Jeep is being worked on as I have an infected foot and can hardly walk.

2001 Jeep Grand Cherokee WJ Laredo 4.0 purchased Sept 2014.
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post #24 of 25 Old 07-14-2020, 11:42 AM
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Quote:
Originally Posted by xjpete View Post
Just wanted to know-why not the Bosch 02 sensors? I know years ago on my Yamaha motorcycle, the Bosch spark plugs didn't work well at all. NGK was OEM spark plugs and really every other plug didn't work right. On the other hand I believe my 97 XJ uses the Bosch 02 sensors. they work fine in there.
On the WJ series Jeep, in addition to other Chrysler products built at the time the one wire pci bus has some problematic data collision issues. You'll read plenty of accounts of DIY repairs that went poorly using the Bosch O2 sensors that were remedied straight away by replacing them with NTK or Denso.

In a shop environment we get them in all the time with running and driveability issues that stem from Bosch O2 sensors on this era of technology and the live data tells the rest of the story the pcm makes undesirable commands to the critical driver circuits based on the data it get's back from them.

You'll see a similar issue with these vehicles with regard to using aftermarket crank position sensors versus the OEM Mopar sensor. Ask anyone on this board and the only recommendation you'll get is the Mopar sensor at any price for a DIY repair.

I use piles of aftermarket crank sensors for tow in's late in the day on a Saturday every year during football season after the dealer parts are long closed for the day. They work fine so long as you own a scan and programming tool that allows the pcm to relearn the operating parameters of the aftermarket sensor.

Without the right tech, they are known to be very problematic for DIY use versus the plug and play Mopar part.
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post #25 of 25 Old 07-14-2020, 04:57 PM Thread Starter
xjpete
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Just wanted to let everyone know my 01 WJ Laredo 4.0 has 4 -02 sensors not 2 like I had thought.

2001 Jeep Grand Cherokee WJ Laredo 4.0 purchased Sept 2014.
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