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Need some serious SMOG help.

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smog
12K views 169 replies 22 participants last post by  Nanookofthenorth 
#1 ·
My YJ has failed 4 times. this last time was after having a new cat and muffler installed. the NO is running at 1314 at 25 mph. I need to know what to do next.
:pullinghair: :surrender:
 
#3 ·
If you have a little time to read go to smogtips.com CA website. It will explain all the readings, the causes and solutions. It was a big help.
 
#7 ·
I had the same problem. Did a tune up, Ran several tanks of cleaner through the gas, marvel miracle oil through the oil, took off my throttle body and cleaned it, took off all the sensors and cleaned or replaced, finally ran Guaranteed to Pass and did an oil change. I did pass. The hardest part was the low speed test, the tester told me it would have done better with stock size tires, it seems to run within the speed and rpm for the test lugged the motor with larger heavier tires,
 
#8 ·
I and retired and realize everyone can't do it, and don't want to be a smarta$$, but I solved all of my CA problems (smog included) when I moved to Tennessee last month.

Hard to beat $3.03/gallon gas and $26 for plates. :iamhappy:

Go :censored: yourself Jerry Brown!!!
 
#9 ·
I and retired and realize everyone can't do it, and don't want to be a smarta$$, but I solved all of my CA problems (smog included) when I moved to Tennessee last month.

Hard to beat $3.03/gallon gas and $26 for plates. :iamhappy:

Go :censored: yourself Jerry Brown!!!
Thats too funny. I would live to solve this issue that way.
 
#10 ·
High NOx.

Caused by being lean. vacuumn leak, exhaust leak, bad O2 sensor.

Engine running too hot, bad thermostat, etc.
 
#11 · (Edited)
NOX is created by excessive HEAT, usually resulting in:
High NOx.
Caused by being lean. vacuum leak, exhaust leak, bad O2 sensor.
Engine running too hot, bad thermostat, etc.
Carbon on the pistons raising compression or holding heat. and a BIG one for our Jeeps, is an exhaust leak anywhere before the cat converter. This works against NOx because the leak acts like Pulse AIR injection, flooding the front half of the cat with O2, preventing it from reducing NOx, then all that O2 goes into the rear of the cat and is burnt up reducing HC and CO, making it difficult to see in the above sample.

Your Jeep is running clean, except for NOx, the other numbers are about where I would expect your 4.0L to be.

My question is: Do you have any exhaust leaks before the cat?
Are you using "Hotter (Rated)" then stock spark plugs?

Have you had a freeze plug replaced since your last smog check?
Lots of "Lazy" Techs will just push the old freeze plug into the block, and pop the new one in over it. creating a hot spot that can result in high NOx numbers.

What I would do if this was MY Jeep:

SEAFOAM! HOT engine, metered into the engine via the brake booster vacuum line, put a restriction in the hose and just barley pull some out of the can until it starts to run funny.
When you have about 1" left in the can, STALL IT by sucking up as much as you can at once
then let it sit about 15 minutes.

This next part is FUN!
DRIVE IT, start out slow and careful, but have fun, you will smoke out your neighbors!

You might want to do this twice.

You might want to change your oil afterwards, there is usually some in the oil that naturally seps past the rings during treatment, but if you have alot of sludge in your oil, drive it a few days first, it will liquefy some of the sludge and clean out your motor (But we NEVER treat our Jeeps like this so there shouldn't be any sludge, right? :tomatoes:)

After you think you are ready, have it re-tested, and please post the result.

Also go back to that tech, he has a good STAR score, showing me he knows his stuff.

Oh, and:
Wait for 2xs to see your post before you take any advice, in the mean time, post up a scan of your results
Thanks!
 
#12 ·
I had my 92' 4.0 smogged by the same tech I believe, he used to be on pirate before he sold his yota. They gave me some sound "advice", even though they aren't able to offer repair or suggested repair. I was high in Nox also, mine was due to a leaky manifold gasket as well as a few leaks just prior to the cat. I replaced the gasket and welded up the leaks, put a new O2 sensor in and brought it back down. I passed at 25mph but actually went up at 15mph compared to when I first went in. Tech asked how far I drove before I showed up, told him it was only about 2 miles and I came in on a whim, he asked me to come back at 8am sharp, don't shut it down and pull straight onto the rollers, had me flog the shit out of it before I showed up.

I passed, not by much but I passed. I think the leaky manifold took its toll on the cat, which is why it barely squeaked by. Have you checked for vacuum leaks, specifically the manifold gasket?

I'm in Elk Grove, let me know if you need a hand with the gasket, I'm a pro at it unfortunatley.
 
#14 ·
I passed, not by much but I passed. I think the leaky manifold took its toll on the cat, which is why it barely squeaked by. Have you checked for vacuum leaks, specifically the manifold gasket?

I'm in Elk Grove, let me know if you need a hand with the gasket, I'm a pro at it unfortunatley.
You aren't far from me. I'll let you know. Thanks.
 
#15 ·
I saw your rig at Starbucks once, recognized it from the pirate thread you posted when it got stolen, glad you were able to recover it. I picked up a new manifold from A1 auto for about $125, don't use the cheap gasket it comes with, it blew out on me 3 months later. Let me know if you need a hand, good luck!
 
#18 ·
this tuesday a buddy and I are going to take the exhaust manifold off and then on wednesday my buddy is going to try to fix the crack and we'll put if back on. we'll see what happens.
 
#19 ·
I don't know if the repair will work, I have read many posts that said the weld just cracked again. Speaking from experience, it would suck to remove everything only to have to do it all over again if the repair doesn't work. My manifold had cracks that couldn't be reached with the tip of the torch even if I tried, i just tossed it out, I would have passed it on if I thought someone could use it.
 
#24 ·
I am not a welder, but when my cast iron exhaust manifold cracked, I replaced it with a header off ebay for under $150. Cast iron is hard to weld on and make it last. The header I purchased was SS and mild steel. It held up 2 years before it cracked. Took it off and had it easily welded back up. Friend did it for free. Cracked exhaust are common on our Jeeps, a friend of mine replaced his with the flex tubing in it and has not had any problems. I didn't get that one because I wanted more of a header than a replacement exhaust manifold. Good luck and let us know how things go.
 
#25 ·
I have a steel exhaust manifold, welded up nicely. helped, but didn't fix the issue. Failed again. NOx is at 1237, about twice what it should be. I've applied for the CAP program here in Cali and we'll see what happens. going to DMV to finish paying registration, get a temp sticker and then Tuesday I'll pay my fixit ticket.
 
#26 ·
ok, been a while since I updated. the welding went really well. got all the cracks filled. smogged it last saturday and still failed, but it dame down. I'm going to do sea foam again with what little I have left. Curious, if it's low on oil, will that make it run hotter?
 
#27 ·
ok, been a while since I updated. the welding went really well. got all the crac Curious, if it's low on oil, will that make it run hotter?
Yes, less oil allows more friction.

But, How low?

Post your new test results please.
 
#29 · (Edited)
Has your CAT ever been replaced?
If it has perhaps they put a '90 instead of a '91 cat accidently (or due to stupidity).

Not common, but I have seen it.
The '90 carbed 4.2 uses an OC+TWC and relies on an EGR to reduce NOx, it has a smaller NOx reduction front half because it relies on that EGR to reduce the majority of the NOx.


http://www.walkerexhaust.com/suppor...onverter/evolution-of-the-catalytic-converter
 
#34 ·
the description on my receipt for the muffler and cat states this: Car sound California certified Pre OBDII Catalytic Converter (EO# D-193-85).
 
#35 · (Edited)
Is there a part number? The part number will give exact applications.

http://www.arb.ca.gov/msprog/aftermkt/devices/amquery.php

Yes, is says except for cats, but this works for non obd2 cats.

EO: D-193-85 View PDFEO Date: 2008-12-04Manufacturer Name: Car Sound Exhaust System, Inc. (d.b.a. Magnaflow)Device: Series 39000 non-OBD II TWCDevice Type: OBD II Catalytic ConverterPart_Number:Model_Specification:Modification_Allowed:Remarks:Series 39000 1995 and older model year pre-OBD II category T-1 trucks None Contact manufacturer or distributor for specific vehicle application
http://arb.ca.gov/msprog/aftermkt/devices/eo/D-193-85.pdf


AND finally:

http://www.magnaflow.com/02catalyti...model=WRANGLER &engine=4.0L&splityear=PRE

Just need that part number...
 
#40 · (Edited)
Lets see, Using the Lambda calculator:

Free Automotive Calculators

1.003 15MPH test 1
1.004 25mph test 1

0.9999 15 MPH test 2
1.003 25 MPH test 2

0.990 to 0.980 is within an acceptable range of 0.98 to 1.02
1.0 perfect for emission and CAT operation (1.005 to 0.995 good for CAT operation)


We know we are in fuel control, the computer is working and doing its job well, but we still have a high NOx issue, so if I was working on your Jeep, the next thing I would do is run a ASM (Dyno) emissions test, in 5 gas ASM mode, and sniff BEFORE the cat.
Why before the cat? the NOx reduction portion of the cat is in front of the TWC, if there is excessive O2 before it will severely reduce the NOx reduction, this gets hidden by the OC reduction portion of the cat using the extra O2 to burn up excess HC and CO, testing before the cat makes this visible.
Basically, our lambda readings are great, but they include what the CAT is burning.
Are you SURE you got all the exhaust leaks?
If so, there could also be a hot spot in the cooling system, If a tech couldnt get a freeze plug out, and pushed it in and put a new one over it, it can cause high NOx from that area, coolant cant flow past the old freeze plug easily, and that spot gets hotter.

Excessive HEAT causes NOx.

You have already run Seafoam, welded cracks in the exhaust.

Are you running stock temp rating/style spark plugs? Hotter ratings can cause NOx issues....

Check your freeze plugs, if any are new, there is a suspect area.
Do you have a stock temp tstat? I know they run those HOT, and that is normal. A cooler Tstat might help a smigon, but i have never seen big results from this.

Maybe take it in COLD, see if you can get him run a cold test.
I seen this work on a V6 Catera, its not legit, but it did make a difference (what fixed the Catera was a AIR pump divert valve, was diverting to exhaust all the time).
 
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