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How to get a cherokee past emissions test?

Old 06-30-2010, 04:27 PM
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Default How to get a cherokee past emissions test?

I just moved to Georgia and had an emissions tests done on my jeep. It failed on the NOX and HC. I replaced plugs,wires and O2 sensor. Then it was worse on the NOX. What am I doing wrong?
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Old 06-30-2010, 05:01 PM
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NOX is caused by high cumbustion temps. Try and run a 70%water to 30% coolant mixture, and Seafoam the intake to clear our any carbon from the cumbustion chambers.
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Old 06-30-2010, 05:10 PM
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What are you doing wrong? Trying to emissions test your Jeep!!

What year is the Jeep?

How is the air filter? That could be causing a lean condition, and raising combustion temps. I would look at the cat converter. HC are exhaust gasses that the cat should filter out.

My best guess

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Old 06-30-2010, 06:56 PM
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Air filter was changed 3 mos ago? Its clean. The only things left are the egr valve and the cat. It doesnt smoke and theres no check engine light.
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Old 06-30-2010, 06:58 PM
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pour the sea foam straight in the intake?? How much???

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Old 06-30-2010, 07:03 PM
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More than likely your cat convertor is no longer doing it's job of reducing nox
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Old 06-30-2010, 07:05 PM
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Thats what I figured. Just to be on the safe side and cover all bases, can I clean the egr valve?
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Old 06-30-2010, 07:09 PM
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If it has one it would not hurt to clean it.
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Old 06-30-2010, 08:13 PM
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Thanks for the input ya'll. I wanted to put a performance muffler on it anyway. I guess I'll replace both while I'm at it
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Old 07-01-2010, 08:20 AM
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The way I used to do it with my old carbureted stuff was, run the tank down as low as possible, dump two gallons of denatured alcohol into the tank, (Keep it off the paint!), reset the idle speed and mixture to keep it running, go to the testing place and amaze them with my near zero emission car that was idling like absolute crapola, stop and fill the tank on the way home and re-reset the carb.

Bonus is the alcohol will get whatever water may be in your tank out as well.

I'm not saying this would work on today's computerized stuff, but it used to work for me.
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Old 07-01-2010, 12:09 PM
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If your Jeep is capable of passing here is how to help it out... LEGALLY


Step #1 give it a tune up (change your oil, replace air filter and PCV valve, replace spark plugs, check wires and distributor cap and rotor button)
Step #2 Use a good fuel injector cleaner 1 tank before testing
Step #3 on testing day drive the car to operating temp preferably a good long freeway drive is best. You want to warm up the catalytic converter to make it perform best.
Step#4 air up the tires. make sure they are at the proper pressure.
Step#5 before testing make sure to turn off everything electrical and make sure the AC is off.


If after all that it still fails you can do a few.... well not illegal things but definitly not recommended things.

#1 remove air filter for testing (puts engine at risk)
#2 back off the adjuster on the rear drums (puts YOU at risk)
#3 air up the rear tires beyond recommended operating pressure (be very careful. Over inflating tires is dangerous!)
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