Help! 1994 Cherokee won't pass smog!
06-30-2009, 03:35 PM
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Help! 1994 Cherokee won't pass smog!
UPDATE: With a new cat installed, the NOx reading were cut in half and the XJ passed smog!!!! Thanks for all the suggestions!
Hey Everyone,
I just bought my first XJ, a cherry 1994 that runs so smooth you would think its new, but much to my dismay I can't get it to pass smog in California.
The previous owner had a new cat and O2 sensor installed 8 months ago. I have changed the plugs, wires, cap and rotor, flushed the coolant, run seafoam through the gas AND through the intake manifold and upper cylinders and went to stock size tires in the back and I still can't get it to pass. I even tried the trick of using denatured alcohol in the gas tank and even that didn't work. The only thing I am failing on is the NOx at 15 mph. I am at my witts end here and really don't want to have to take it to a shop to get fixed so if there is anything I am over looking please let me know.
The results were as follows:
15 MPH (1621 RPM)
%O2 = .1
%CO2 = 14.7
HC MAX = 89 Meas = 9 PASS
%CO MAX = .66 Meas = .07 PASS
NO MAX = 517 Meas = 643 FAIL
25 MPH (1614 RPM)
%O2 = .1
%CO2 = 14.6
HC MAX = 54 Meas = 8 PASS
%CO MAX = .80 Meas = .07 PASS
NO MAX = 770 Meas = 655 PASS
Thanks in advance for any insight!
John
Hey Everyone,
I just bought my first XJ, a cherry 1994 that runs so smooth you would think its new, but much to my dismay I can't get it to pass smog in California.
The previous owner had a new cat and O2 sensor installed 8 months ago. I have changed the plugs, wires, cap and rotor, flushed the coolant, run seafoam through the gas AND through the intake manifold and upper cylinders and went to stock size tires in the back and I still can't get it to pass. I even tried the trick of using denatured alcohol in the gas tank and even that didn't work. The only thing I am failing on is the NOx at 15 mph. I am at my witts end here and really don't want to have to take it to a shop to get fixed so if there is anything I am over looking please let me know.
The results were as follows:
15 MPH (1621 RPM)
%O2 = .1
%CO2 = 14.7
HC MAX = 89 Meas = 9 PASS
%CO MAX = .66 Meas = .07 PASS
NO MAX = 517 Meas = 643 FAIL
25 MPH (1614 RPM)
%O2 = .1
%CO2 = 14.6
HC MAX = 54 Meas = 8 PASS
%CO MAX = .80 Meas = .07 PASS
NO MAX = 770 Meas = 655 PASS
Thanks in advance for any insight!
John
Last edited by Goathearder; 07-11-2009 at 11:07 AM.
06-30-2009, 05:11 PM
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i got nothing it sounds like every thing has been replaced that i can think of have you tried running some of the stuff you can get at the auto parts store to help you pass it and do the spark plugs look good when you pull them are they in good shape and color what type are they sorry i am just think out loud here how is the timing set on the motor
06-30-2009, 05:26 PM
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you know its easy to bash California but the thing should be running good regardless what state you are in weather it be Oklahoma or Florida or caliey he needs help not just get out of California
06-30-2009, 05:28 PM
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i got nothing it sounds like every thing has been replaced that i can think of have you tried running some of the stuff you can get at the auto parts store to help you pass it and do the spark plugs look good when you pull them are they in good shape and color what type are they sorry i am just think out loud here how is the timing set on the motor
I am wondering if the cat could be bad already.
Does anyone know how to read the numbers to tell me if I am running too lean?
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06-30-2009, 05:31 PM
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no i cant really read them that good but i would think that it could be running a tad rich but i am not sure i know there are some who can help you with it
06-30-2009, 05:51 PM
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Year: 1987
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Engine: 4.0 Renix HO. head
Are you sure that the old owner Put a ligit cat on it? When is the last time you changed your oil... OIl changes before sniffer tests helps a bit.... Check your PVC lines and make sure that they are clear and working. Pvc would raise Nox levels if its clogged.
Just passed my sniffer test but my Hydrocarbons was high and My cat was clogged.
Just passed my sniffer test but my Hydrocarbons was high and My cat was clogged.
06-30-2009, 05:58 PM
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you know its easy to bash California but the thing should be running good regardless what state you are in weather it be Oklahoma or Florida or caliey he needs help not just get out of California
USE PUNCTUATION!!!
06-30-2009, 06:02 PM
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Are you sure that the old owner Put a ligit cat on it? When is the last time you changed your oil... OIl changes before sniffer tests helps a bit.... Check your PVC lines and make sure that they are clear and working. Pvc would raise Nox levels if its clogged.
Just passed my sniffer test but my Hydrocarbons was high and My cat was clogged.
Just passed my sniffer test but my Hydrocarbons was high and My cat was clogged.
I read some stuff elsewhere about using colder heat range spark plugs so I might try that as well.
06-30-2009, 06:05 PM
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06-30-2009, 06:11 PM
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sorry cant and i was just saying that he wanted help not get out of the state. and i was not being mean just trying to make sure he got help not the start of a why is California bad thread again
06-30-2009, 06:23 PM
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Year: 1989
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i had a problem with mine 2
the cat was 6 month old
and the o2 sensor 2
i took it to the mech.and he told me this,
replace the cat and the o2 sensor but first replace the computer on it because it was not reading the o2 sensor, i did it ,and it pass
but before you do all this check the wire on the o2 sensor (damage)
and for the cat if it's dirty, it is and it wont pass
because i did everything 1 by 1 trying 2 save money
the cat was 6 month old
and the o2 sensor 2
i took it to the mech.and he told me this,
replace the cat and the o2 sensor but first replace the computer on it because it was not reading the o2 sensor, i did it ,and it pass
but before you do all this check the wire on the o2 sensor (damage)
and for the cat if it's dirty, it is and it wont pass
because i did everything 1 by 1 trying 2 save money
