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Old 02-06-2013, 08:15 PM   #1
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Trying to pass smog

94 Yj 4.0L I failed smog 2x the diagnostic came up as bad cat and O2 sensor so I replaced them both. Failed smog again for high NOx diagnostics said bad cat. The shop told me I need a new original cat not an aftermarket cat. I took it to another shop they found a crack in the exhaust manifold so I replaced that took it back to continue the diagnostics and they came up with a bad cat.

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Old 02-06-2013, 08:17 PM   #2
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I then spoke with Walker who makes the cat and they say that it's not the cat and that the jeep is running too lean. How do I if this

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Old 02-06-2013, 08:21 PM   #3
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[QUOTE="Skyhawk"]I then spoke with Walker who makes the cat and they say that it's not the cat and that the jeep is running too lean. How do I fix this
Any suggestions and or knowledge is greatly appreciated
I've done all the work myself to save on labor but now the parts are adding up and no solution had been found
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Old 02-06-2013, 08:29 PM   #4
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For the DIY guys a page with everything you need to know about passing a smog. It is worth a read and I am not real smart on all this but this is where I came to fix mine.

Failed Emissions Test. My car failed the emissions test - SmogTips.com.
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Old 02-06-2013, 08:31 PM   #5
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High nox is caused by high combustion temps. Get those temps down and the nox will follow. (Water injection comes to mind). Check your local laws regarding tampering with emissions before you try anything crazy. GL.
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Old 02-06-2013, 08:41 PM   #6
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Thanks
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Old 02-06-2013, 08:54 PM   #7
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Is it idling a little high as well? An intake leak somewhere could cause it to run lean. Usually accompanied by higher than normal idle speed. Is it carbed or injected? Either could be starving a little on fuel -- not enough to stall, but enough to be too lean.
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Old 02-06-2013, 11:47 PM   #8
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4.0L are always FI from the factory, so unless the OP changed the intake to a measly carb setup, then it's FI.
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Old 02-07-2013, 03:50 PM   #9
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Yes it's injected

Any other suggestions as to why the thing runs lean an has high NOx
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Old 02-07-2013, 06:17 PM   #10
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If you are close make sure that right before you get it tested that you are getting the exhaust really hot, the cat converter does not work correctly until it gets super hot.

I always go burn down the a couple exits on the freeway right before I go get my test done.
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Old 02-08-2013, 12:56 AM   #11
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Exhaust leak before the cat will kill the NOx portion of the converter.
Im surprised you actually believed that a OEM cat would make a difference, anyone who says that is incompetent, never go back to that shop.

Do you have the correct spark plugs (temp rating too high will cause high NOx).
Excessive carbon on the pistons will cause higher compression, If your Jeep has high miles, perform a Top Engine Clean service, basically this knocks the carbon off the pistons and combustion chambers and restores compression to stock (does a damm good job cleaning the valves off too).

Jerricho normal operating temp, over/Superheating his Jeep will cause the NOx to go up, NOx is produced by excessive heat....
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Old 02-09-2013, 12:01 AM   #12
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How much should that be to have done?
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Old 02-09-2013, 12:31 AM   #13
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Old 02-09-2013, 04:28 PM   #14
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Old 02-09-2013, 04:38 PM   #15
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Quote:
Originally Posted by 2xs
Exhaust leak before the cat will kill the NOx portion of the converter.
Im surprised you actually believed that a OEM cat would make a difference, anyone who says that is incompetent, never go back to that shop.

Do you have the correct spark plugs (temp rating too high will cause high NOx).
Excessive carbon on the pistons will cause higher compression, If your Jeep has high miles, perform a Top Engine Clean service, basically this knocks the carbon off the pistons and combustion chambers and restores compression to stock (does a damm good job cleaning the valves off too).

Jerricho normal operating temp, over/Superheating his Jeep will cause the NOx to go up, NOx is produced by excessive heat....
I did not believe that the OEM cat would work and thanks for confirming that again.
I am going to start with cleaning and replacing a few sensors that are cheap and since it is needed any way the radiator. It's old and on its last life looking, still working just not confident in its longevity
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Old 02-09-2013, 04:48 PM   #16
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I've heard of a product called "cata clean" which help clean your catalytic converter. I'm no mechanic or anything of sort but maybe that might just do it for a quick fix for your emmission test until you figure out the main issue.
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Old 02-09-2013, 10:30 PM   #17
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Your CO2 is fine, your cat is fine.
CO2 should be 14.7% ideally, but during the actual test its high enough, and you are running fine, What I see is ALOT of O2.

Does your exhaust manifold leak? or is there ANY leak before the cat? If so, fix that first, an exhaust leak will flood the converter with O2 preventing it from separating the O2 from the NO ending up with higher NOx.
Look at the printouts, the lower your O2 is, the lower your NOx is...

NOx is created by HEAT, Excess carbon in the pistons creating higher compression results in hotter burn and NOX creation.
An O2 biased rich telling the computer to lean out the mixture causes higher burn temps (A leaner mixture burns hotter), ending in high NOx.

But im guessing you have an exhaust leak before the converter, this is COMMON on these engines, so if you dont, let me know and Ill tell you about more money you can spend.

Remember this also, you are taking your Jeep to a TIRE SHOP, they are stupid.
I LOL'D at the first image you posted, it says EGR can be a symptom, we all know the 4.0 has NO EGR!

Then I looked at the smog tech, hes new, wet behind the ears with NO experience, and might do 3 smogs a month:
http://www.smogcheck.ca.gov/pubwebqu...px?tech=632709
and the second guy has worked everywhere, probably cant hold a job down:
http://www.smogcheck.ca.gov/pubwebqu...tech_no=634014
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Old 02-10-2013, 03:31 AM   #18
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I failed my first smog test and here are the things I did to get the temp down and pass.

- Replaced spark plugs
- Checked all spark plug wires for good continuity
- Replaced the cap and rotor (this was not bad but felt it was worth the change)
- Checked the fuel rail for good pressure (35psi)
- I have a cold air intake removed and cleaned 2x to make sure.
- Checked for any exhaust leaks (did not find any)
- Ran high octane gas with injector cleaner for a week (2 bottles of clean and two fill ups.
- Oil change (made sure my oil was topped off before going back)
- Replaced the fuel filter

I passed and brought down my C02 and NOx by half.

I have 92 Wrangler with 4.0L

Good Luck
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Old 02-10-2013, 01:32 PM   #19
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The exhaust manifold had a crack in it and i replaced it with a new one for 200$. I had it tested after it was replaced and the second shop i took it to said the same thing bad cat need a factory cat.The second shop is not a tire shop but dont seem to know much more.
I also replaced the plugs and wires, changed the oil and filter, and put seafoam through the thing and still they are saying bad cat. All this was done prior to me starting this thread

And again all help is greatly appreciated
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Old 02-12-2013, 11:24 AM   #20
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Quote:
Originally Posted by 2xs
Your CO2 is fine, your cat is fine.
CO2 should be 14.7% ideally, but during the actual test its high enough, and you are running fine, What I see is ALOT of O2.

Does your exhaust manifold leak? or is there ANY leak before the cat? If so, fix that first, an exhaust leak will flood the converter with O2 preventing it from separating the O2 from the NO ending up with higher NOx.
Look at the printouts, the lower your O2 is, the lower your NOx is...

NOx is created by HEAT, Excess carbon in the pistons creating higher compression results in hotter burn and NOX creation.
An O2 biased rich telling the computer to lean out the mixture causes higher burn temps (A leaner mixture burns hotter), ending in high NOx.

But im guessing you have an exhaust leak before the converter, this is COMMON on these engines, so if you dont, let me know and Ill tell you about more money you can spend.

Remember this also, you are taking your Jeep to a TIRE SHOP, they are stupid.
I LOL'D at the first image you posted, it says EGR can be a symptom, we all know the 4.0 has NO EGR!

Then I looked at the smog tech, hes new, wet behind the ears with NO experience, and might do 3 smogs a month:
http://www.smogcheck.ca.gov/pubwebqu...px?tech=632709
and the second guy has worked everywhere, probably cant hold a job down:
http://www.smogcheck.ca.gov/pubwebqu...tech_no=634014
I guess you can go ahead and tell me about more money to spend.
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Old 02-12-2013, 03:10 PM   #21
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Quote:
Originally Posted by GoNeMaD View Post
I failed my first smog test and here are the things I did to get the temp down and pass.

- Replaced spark plugs
- Checked all spark plug wires for good continuity
- Replaced the cap and rotor (this was not bad but felt it was worth the change)
- Checked the fuel rail for good pressure (35psi)
- I have a cold air intake removed and cleaned 2x to make sure.
- Checked for any exhaust leaks (did not find any)
- Ran high octane gas with injector cleaner for a week (2 bottles of clean and two fill ups.
- Oil change (made sure my oil was topped off before going back)
- Replaced the fuel filter

I passed and brought down my C02 and NOx by half.

I have 92 Wrangler with 4.0L

Good Luck
You brought your CO2 down? that is supposed to be 14.7% ideally....
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'04 SV1000s:
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Old 02-12-2013, 03:25 PM   #22
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Originally Posted by Skyhawk View Post
I guess you can go ahead and tell me about more money to spend.
Have you ever replaced a freeze plug? couldnt get it out, so pushed it into the block and popped a new one in over it?
That is a hot spot that WILL raise your NOx.
Are you 100% positive you have the right heat range spark plugs? if its hotter then stock, that is a NOx creator.

More fuel = less NOx, fuel actually cools the process, make sure your fuel filter is ok, maybe (only for the test) hide a BB in the Fuel pressure regulator line, this will fatten up the mixture (I did NOT tell you this, its defeating the FPR, but is a way I test its operation).

Might be time for a Top Engine clean service (Carbon in the pistons will raise compression and raise NOx), go buy 2 cans of Sea Foam, (this helps if you have a Mechanic friend help you), With the engine HOT and running about 1500 RPS, pull a manifold vacuum line, and dip it onto the TOP of the sea foam liquid so you only pull a small amount of liquid, let it pull the RPM down about 400-600 RPM without stalling it, Stalling it is BAD, potential hydro-locking the engine, SO BE CAREFULL (once you have done it, it becomes easy). Near the end of the bottle/can, let it stall it and let is sit about a half hour, then go start it up, IT WILL SMOKE ALOT!
Go drive it, smoke out your neighborhood, its fun!

What is the C.A.R.B. # on your cat? D ###-## is what a am after.
I suppose you have a defective new cat, but that is RARE!
Make sure that number matches your Jeep:
Database: Aftermarket Parts Database of Executive Orders
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Old 02-13-2013, 12:44 AM   #23
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I used sea foam already an so far I've changed:
Catalytic converter
Plugs/wires
Distributor
Rotor
Exhaust manifold (had a crack)
Oil/filter
Radiator(had stop leak in it for pin hole)
Map sensor
Air charge temp sensor
Fuel cap
O2 sensor
PCV valve
Tomorrow I will change the fuel filter( I ran out of time today)
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Old 02-13-2013, 01:07 AM   #24
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Find a shop that will "pass" you...I hate cali.
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Old 02-13-2013, 01:22 AM   #25
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Get a po box in sanora ca no smog law you only smog it once and never again your entire life that's what i did and then a motor swap chp can't do anything about it no bar and reff rules
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Old 02-13-2013, 02:05 AM   #26
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Quote:
Originally Posted by 2xs View Post
You brought your CO2 down? that is supposed to be 14.7% ideally....
Yeah my CO2 was 26.2 in az 20 is the number to beat. I dropped to 16.4 I was really surprised.
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Old 02-13-2013, 02:09 AM   #27
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Originally Posted by jonchancey92 View Post
Get a po box in sanora ca no smog law you only smog it once and never again your entire life that's what i did and then a motor swap chp can't do anything about it no bar and reff rules
Ive heard of something like that but didn't think it would actually work
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Old 02-13-2013, 02:11 AM   #28
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It works me and counts of my buddys have done it my 2007 1994 1992 and srt4 are registered there i live in Modesto ca drive there to get my new tags every year lol you should do it po box only 56bucks a year
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Old 02-13-2013, 11:39 AM   #29
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Quote:
Originally Posted by jonchancey92
It works me and counts of my buddys have done it my 2007 1994 1992 and srt4 are registered there i live in Modesto ca drive there to get my new tags every year lol you should do it po box only 56bucks a year
That's a 6-7 hour drive for me but might make for a good excuse to take a road trip
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Old 02-13-2013, 07:55 PM   #30
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So I finally passed and so thanks to all the input and suggestions from everyone
I appreciate the help and happy trails

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