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Unread 08-11-2013, 03:45 PM   #1
mancha
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Join Date: Jul 2012
Location: Albuquerque, NM
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Failed Emissions.....Need Help

Sorry for another Emissions thread polluting general pop but I searched and couldn't find the answers I need.

It's a '94 4.0L engine with 194K on the clock. I'm running over the limit in HC and CO2.

So far I've replaced the O2 sensor and the PO replaced the spark plugs and cap. Emissions guy said if I ran an injector cleaner and higher octane fuel it might be enough to get me a passing because I'm barely failing.

What should check I next?

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Unread 08-11-2013, 04:15 PM   #2
Mark05059
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run your tank till its about 1/2 full and dump a pint of seafoam into the tank.. drive it till its 1/4 full and then fill up with high octane fuel... then with the jeep engine warmed up go take the test again.
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Unread 08-11-2013, 09:46 PM   #3
harryi
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Using a lazer thermometer check the cat inlet and outlet temp. You may need a new cat.
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Unread 08-12-2013, 08:31 PM   #4
mancha
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Should the temps be different or the same?
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Unread 08-12-2013, 08:36 PM   #5
jepnbyu
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I had a similar problem on my 93 YJ. The tester said it was the cat and wanted to sell me one. I had replaced it four or five years prior and used the lifetime warranty and passed with no problems. 2 years later I put an O2 sensor in it and passed. Run premium fuel and get it real hot before you take it in.
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Unread 08-12-2013, 09:17 PM   #6
harryi
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The inlet temp should be much lower than the outlet temp. This means the cat is doing its job if more than 100F
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Unread 08-16-2013, 05:47 PM   #7
Robob69
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1995 YJ Wrangler 
 
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Location: Sugar Land, Texas
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Ok.. I had the same issue.. Failed 5 times in one day.. I changed:
Cat Converter
All Vacuum Lines
Plugs
Wires
Cap and Rotor
Even drained the Radiator and refilled with new Anti-Freeze
Changed the oil..
Tried the Pass emissions treatment.
I finally changed the Fuel Injectors
Still nothing..
Changed the Fuel Pressure Regulator and BAM!!! Fixed it.. Was reading High NoS
Now perfect..
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Unread 08-17-2013, 03:40 PM   #8
mancha
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Think it was just the pressure regulator that fixed it? How much is it and how hard of an install?
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Unread 08-20-2013, 05:03 AM   #9
Robob69
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I think it was around $45.. I checked the pressure at the parts house with a gauge at it was way off. Changed the regulator and bam pressure was within limits. Ran better too.
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