95 4.0 YJ failed Emissions. - JeepForum.com
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Unread 04-11-2013, 10:18 AM   #1
Robob69
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95 4.0 YJ failed Emissions.

Grrrrr..

I drive in to get a quick inspection and wind up sitting here forever..

High Nox.

Last year after I bought the jeep it failed.
New plugs, wires, cap and rotor.
New Cat converter. New muffler.

All other numbers are golden...

So now they say.. Since I dont drive it much that is causing the cat converter to not stay clean and causing issues.
Damaged O2 sensor from a rock in Arkansas mountains.

So will try again after cat and O2 sensor.

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Unread 04-11-2013, 10:21 AM   #2
superj
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dang, if its no good, register it down here and do our visual inspection. we don;t have to pass any readers.

or, you could donate it to the superj saves jeeps foundation
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Unread 04-11-2013, 10:27 AM   #3
Robob69
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I hate this emissions crap... just another way to get that hard earned $$$ from us..
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Unread 04-11-2013, 10:51 AM   #4
Que89YJ
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ROBO wait! If you are running high NOX then you are running lean. The O2 and cat will cause it to run rich. You do need to look at the cat and O2 if they were damaged but the O2 will cause a rich condition usually. Check and replace the O2 sensor and while you are at it check your fuel pressure. 31psi idle and 39 psi with the vacuum line pulled from the fuel regulator.
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Unread 04-11-2013, 11:04 AM   #5
Robob69
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How do I check the pressure?
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Unread 04-11-2013, 11:15 AM   #6
Robob69
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Was juat told the cat was all rusted up inside and that I let the jeep sit too long is the cause. I only drive it on thw weekends and it sits a lot. They are putting the O2 sensor on now and then retest..
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Unread 04-11-2013, 11:52 AM   #7
Que89YJ
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The cat could be the issue. The rail pressure is under the hood on the injector manifold. You get a guage from the local parts store. The big ones have tool lend programs that allow you to borrow a tool for a job by putting down a fully refundable deposit. Post back if the Cat and O2 sensor doesn't fix it.
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Unread 04-11-2013, 12:05 PM   #8
Robob69
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Will do... They about to run it now... Lets hope....
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Unread 04-11-2013, 12:24 PM   #9
Robob69
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FAILED AGAIN..... Nox went down slightly for low speed and way up for high speed...
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Unread 04-11-2013, 01:05 PM   #10
Que89YJ
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You need to run the fuel test. 31 psi idle, 39 psi with the vacuum line to the fuel regulator removed.
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Unread 04-11-2013, 01:49 PM   #11
Robob69
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Ok.... well before I get to that.. I found a major vacuum leak at the booster and fixed them... Going to test one more time.. what will the pressure test tell me?
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Unread 04-11-2013, 02:42 PM   #12
Siva283
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The pressure test will help you figure out if you are getting to much to little or the proper amoiunt of fuel. Its a big peice to the puzzle. As Que pointed out. High NOx is normally from a lean condition. I think an engine running hot can cause this as well. How is your temp?
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Unread 04-11-2013, 02:44 PM   #13
Robob69
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Temp guage looks ok.. thwey are checking now..
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Unread 04-11-2013, 04:23 PM   #14
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OK.... The Shop Did not check fuel pressure.... Kept saying that has nothing to do with it... I insisted and still no.. So I left...
The NOx would be perfect in the 200-300 range and then when RPM's come up around 1300 they shoot way up to 2400-3500.
The engine runs smooth.... No issues but when at idle it does have a slight miss.

Work done today is:

New Cat Converter
New O2 Sensor
Drained and flushed Radiator
Added Seafoam to fuel and filled up with Super Unleaded
Ran 3 Tests and all failed way bad...

Not looking good...

Even the tech doing the test was amazed that it runs so good and still will not pass.

They are telling me that I need to clean my intake out due to carbon.... Would not be a LEAN issue then...

Anyone...

I will check on a fuel pressure gauge in about an hour..
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Unread 04-11-2013, 05:12 PM   #15
Robob69
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I have a gauge now and it reads 40 psi regardless of vacuum..

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