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Unread 07-11-2013, 09:54 AM   #31
bmxboy809
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Quote:
Originally Posted by sc00bz View Post
If you get no stumble with the back one unplugged, unplug the back one for a day and zip tie the harness out of the way. If no stumble, replace the back one.

By back one, I mean the downstream. Your symptoms are quite similar to when my upstream went out. I don't see why it wouldn't work the same way as when I tested my upstream.
I definately could do this. I get the same result by unplugging every other sensor too. As long as the CEL is on it runs ok. The only thing that turns on the CEL is a missing sensor.

I think I will bite the bullet and replace both O2 sensors tonight. If it fixes the problem I will be happier than a pig in ****! If not then I will have to keep buying sensors till it goes away

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Unread 07-11-2013, 10:59 AM   #32
sc00bz
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Quote:
Originally Posted by bmxboy809 View Post

I definately could do this. I get the same result by unplugging every other sensor too. As long as the CEL is on it runs ok. The only thing that turns on the CEL is a missing sensor.

I think I will bite the bullet and replace both O2 sensors tonight. If it fixes the problem I will be happier than a pig in ****! If not then I will have to keep buying sensors till it goes away
Just be sure to get NTK. FYI they are A LOT cheaper on rockauto than a parts store.

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Unread 07-11-2013, 10:15 PM   #33
mukluk
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Not necessarily answering your question from earlier, but hopefully at least helping you understand the O2 sensor outputs a bit more...

The O2 sensors' normal operational range is roughly 0.2 to 1.5 volts; the lower the output the leaner the engine is burning, following logically therefore the higher voltage results from richer burning. When your catalytic convertor is operating as it should, the downstream sensor will read lower than the upstream. As the cat ages and loses efficiency, the downstream sensor output will eventually match that of the upstream sensor -- when that occurs the PCM will throw a code for cat efficiency.

It doesn't make much sense that unplugging the downstream sensor would clear up your running problems, unless maybe its output is screwing things up for the upstream sensor.
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Unread 07-12-2013, 09:45 AM   #34
bmxboy809
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I removed both O2 sensors but as usual the threads were all jacked up. I have been wanting a high-flow Cat to complete the rest of my new exhaust so I have a new Magnaflow downpipe and cat in the mail along with the new O2 sensors. Hopefully this will help fix the problem but if not I guess that will be this summers mod instead of a winch.

I stopped at the local Jeep shop to check on a used computer, the guy there said he may have one on the shelf I can get pretty cheap. If its cheap enough I might try that next. If he comes back with a rediculous price then maybe MAP sensor is next.
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Unread 07-13-2013, 04:33 AM   #35
pfifer
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Have you tried replacing your Throttle Positioning Sensos yet? When mine went bad my Jeep did much the same thing your is doing.
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Unread 07-15-2013, 08:15 AM   #36
bmxboy809
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Quote:
Originally Posted by pfifer View Post
Have you tried replacing your Throttle Positioning Sensos yet? When mine went bad my Jeep did much the same thing your is doing.
Did you test yours first? I have tested mine with a meter and the closed throttle and WOT voltages were within spec and the needle on my meter moved smooth with no jumps or flat spots. I also used the Torque app on my phone to watch the voltage curve and it gave the same result as feedback from the PCM. Everything indicates the sensor is fine EXCEPT that it still runs like crap.

i will get the new O2 sensors in this week and see what happens
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Unread 07-15-2013, 06:10 PM   #37
sc00bz
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Quote:
Originally Posted by bmxboy809 View Post

Did you test yours first? I have tested mine with a meter and the closed throttle and WOT voltages were within spec and the needle on my meter moved smooth with no jumps or flat spots. I also used the Torque app on my phone to watch the voltage curve and it gave the same result as feedback from the PCM. Everything indicates the sensor is fine EXCEPT that it still runs like crap.

i will get the new O2 sensors in this week and see what happens
I hope it works out for you. I'm quite literally at a loss without being able to be there to perform voltage tests myself. I honestly doubt it's an o2 sensor which is why I suggested the unplugging and running for a day experiment without buying beforehand when you suspected an oddity. However, I have been wrong before.

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Unread 07-16-2013, 07:40 AM   #38
bmxboy809
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Quote:
Originally Posted by sc00bz View Post
. I honestly doubt it's an o2 sensor which is why I suggested the unplugging and running for a day experiment
I didnt run this way for a whole day but I did try this several times. Unplugging the O2 sensor caused the CEL to come on (as it should) and as long as the light is on it runs pretty good (same result if I unplugged the Coolant temp). I am at a total loss for the next move as well. The only thing that seemed to have an odd result was unplugging that downstream sensor. At 140k miles I am not suprised the sensors would need to be replaced, but i am not convinced it will solve the problem.

Is there a way I can make sure the computer is working right? I watched all the sensor feed back in Torque, and thought if a bunch of sensors looked wacky then there is a good chance the PCM was toast. If i take it to a dealer or something will their dignostic tools be able to tell for sure?
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Unread 07-16-2013, 09:17 AM   #39
sc00bz
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Quote:
Originally Posted by bmxboy809 View Post

I didnt run this way for a whole day but I did try this several times. Unplugging the O2 sensor caused the CEL to come on (as it should) and as long as the light is on it runs pretty good (same result if I unplugged the Coolant temp). I am at a total loss for the next move as well. The only thing that seemed to have an odd result was unplugging that downstream sensor. At 140k miles I am not suprised the sensors would need to be replaced, but i am not convinced it will solve the problem.

Is there a way I can make sure the computer is working right? I watched all the sensor feed back in Torque, and thought if a bunch of sensors looked wacky then there is a good chance the PCM was toast. If i take it to a dealer or something will their dignostic tools be able to tell for sure?
I want to say there is a way to test it in the FSM using an ohm meter on different pinouts but I'm not 100% sure and being at work on my phone, I don't have a copy with me.

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Unread 07-16-2013, 09:34 AM   #40
bmxboy809
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I will take a look at the FSM to see if there is a way to check it out.

I read another post with the same issues so I will ad a few more details...
  • I replaced the cylinder head last summer so the intake manifold gasket is new and should be fine, I have not yet tried the carb cleaner trick but I will. I made sure to use a gasket with the raised metal rings around the ports when i replaced the exhaust manifold. because I had trouble with the flat kind.
  • The battery looks kinda old and I noticed corrosion on the bolt through the positive clamp. The battery passed a load test around christmas time and I have not had any battery related problems.
  • Oil pressure gauge sometimes reads normal and sometimes is pegged at 80psi. It has always been this way since I bought it last winter
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Unread 07-16-2013, 10:39 AM   #41
AtomicDog
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I've seen problems on other vehicles when they warm up and the EGR opens. When cold the EGR is not in the loop. Just a thought.
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Unread 07-16-2013, 11:22 AM   #42
bmxboy809
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'91 and up do not use EGR but have a three way cat instead. Thanks for the input tho
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Unread 07-16-2013, 10:44 PM   #43
ipath68
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So are you guys replacing o2 sensors without getting codes? I know my jeep is running rich and I just changed plugs, injector o rings, and it didn't do anything. I had the tail piece of my exhaust replaced and it is super coated in black now. My head pipe has been replaced with the mini cats so my thought was o2 sensors? Not trying to hi jack I just see people saying replaced o2 sensors.
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Unread 07-17-2013, 07:25 AM   #44
sc00bz
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Quote:
Originally Posted by ipath68 View Post
So are you guys replacing o2 sensors without getting codes? I know my jeep is running rich and I just changed plugs, injector o rings, and it didn't do anything. I had the tail piece of my exhaust replaced and it is super coated in black now. My head pipe has been replaced with the mini cats so my thought was o2 sensors? Not trying to hi jack I just see people saying replaced o2 sensors.
TJs are notorious for having o2 sensors go out and not throwing a CEL. Hence why the test.

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Unread 07-17-2013, 09:14 PM   #45
bmxboy809
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Quote:
Originally Posted by ipath68 View Post
So are you guys replacing o2 sensors without getting codes?
I just did and it seemed to do the trick! I replaced both o2 sensors as well as the cat and downtube. I watched in Torque and the o2 sensor feedback was much more believable. I saw downstream numbers greater than .1 or 0 and i saw both go to 0 on decell.

After some drive time to heat everything up, the sputter/stumble/hesitation seems to be gone after changing both sensors and the cat. The catalytic converter may have been ok but now my exhaust is complete. Hopefully this is the end this problem. If not you can be sure I will have more questions
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