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Old 03-11-2013, 03:00 PM
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Originally Posted by tssguy123

Bah. So now I have to get a vacuum gauge and test it... someone told me that if I could hear a noise underneath then my cat could be bad?
What year is your jeep?
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Old 03-11-2013, 03:01 PM
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Originally Posted by odgreen89on35s
What year is your jeep?
1996.
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Old 03-11-2013, 03:02 PM
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Originally Posted by lowrange2
I used 1/4" x 3" flat stock. Cut and weld. Done. Cost 8 bucks.
Yea but as an American I need a name brand product for it tie quality lolololol. Maybe ill do that. Was the flat stock able to bend at the corners
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Old 03-11-2013, 03:03 PM
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Originally Posted by ccooper1234
OK I did the cowl intake this weekend but now km getting 12 MPG. I was getting 17 before. Its all stock except for a front bumper. What's wrong?
Put it back stock for a day or two and see if it goes back up. What size intake did you use?
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Old 03-11-2013, 03:03 PM
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Originally Posted by odgreen89on35s
What year is your jeep?
96. Cruiser said that in order to test it I hook up a vacuum gauge to manifold and rev up to ~2500 for about 20 seconds and then let the throttle snap shut blah blah I'm sure you already know.
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Old 03-11-2013, 03:03 PM
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Originally Posted by sycoglitch
Yea but as an American I need a name brand product for it tie quality lolololol. Maybe ill do that. Was the flat stock able to bend at the corners
If you have a press, sure. Mine are flat. No bends in the corner.
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Old 03-11-2013, 03:06 PM
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Originally Posted by lowrange2

If you have a press, sure. Mine are flat. No bends in the corner.
K thanks
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Old 03-11-2013, 03:06 PM
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Originally Posted by tssguy123

96. Cruiser said that in order to test it I hook up a vacuum gauge to manifold and rev up to ~2500 for about 20 seconds and then let the throttle snap shut blah blah I'm sure you already know.
You have a check engine light? First year of obd2. If yhe cat was bad it would have a check engine light.
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Old 03-11-2013, 03:08 PM
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Originally Posted by odgreen89on35s
You have a check engine light? First year of obd2. If yhe cat was bad it would have a check engine light.
From what I've heard it could be clogged without a CEL, but no, I don't have a CEL.. something is giving me this 11mpg and I'm just going down the list. :P
Actually now that you mention it... I guess 96s do have a downstream O2 which would tell me if I had a bad cat.... wouldn't it?
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Old 03-11-2013, 03:34 PM
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Originally Posted by lowrange2
GOOD JOB!

Your day going better, Mr Sunshine? LOL.
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Old 03-11-2013, 03:37 PM
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Originally Posted by tssguy123
96. Cruiser said that in order to test it I hook up a vacuum gauge to manifold and rev up to ~2500 for about 20 seconds and then let the throttle snap shut blah blah I'm sure you already know.
$20 vacuum gauge works wonders. I don't trust CELs for clogged exhaust.
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Old 03-11-2013, 03:39 PM
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Originally Posted by tssguy123
From what I've heard it could be clogged without a CEL, but no, I don't have a CEL.. something is giving me this 11mpg and I'm just going down the list. :P
Actually now that you mention it... I guess 96s do have a downstream O2 which would tell me if I had a bad cat.... wouldn't it?
It's common for the rare earth element matrix to come loose in XJ factory cat's ...there was even a recall at one point. Just tap the thing with SFH; if you hear the rattle, it's dead ...its a broken matrix. You might NOT get a CEL; just depends. (I got one a couple of times. After a reset, it would go away for awhile. Stupid ECU.)

...and yeah, 11mpg is one possible indicator for a bad cat'.

...and yes, the '96 has a downstream sensor.

DON'T THROW THE OLD CAT' AWAY. A recycler will pay you up to $75 for a full-size cat' (for the rare earth elements). Google it; there's likely one near you.
Last edited by brdavis9; 03-11-2013 at 03:42 PM. Reason: added sensor info
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Old 03-11-2013, 03:40 PM
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Originally Posted by tssguy123

From what I've heard it could be clogged without a CEL, but no, I don't have a CEL.. something is giving me this 11mpg and I'm just going down the list. :P
Actually now that you mention it... I guess 96s do have a downstream O2 which would tell me if I had a bad cat.... wouldn't it?
For the sake of argument, it depends: The PCM throws a CEL if the downstream O2's reading is identical or 'too close' to the upstream's. If one or both are screwed then the PCM will think the cat is working normally.

You can also do a quick check with an IR thermometer. A properly functioning catalytic converter's exhaust will be several hundred degrees hotter than the gasses going in. (on phone at a curry house right now so not sure of the actual numbers)
Last edited by salad; 03-11-2013 at 03:42 PM.
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Old 03-11-2013, 03:47 PM
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Originally Posted by cruiser54
$20 vacuum gauge works wonders. I don't trust CELs for clogged exhaust.
Alright alright, I'll get one. I need to get one anyway so I can drive more economically I guess. Thanks Cruiser.

Also, Thanks Salad. An IR thermometer is something I do have!
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Old 03-11-2013, 03:53 PM
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Originally Posted by lowrange2

Put it back stock for a day or two and see if it goes back up. What size intake did you use?
This is what I made.
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