Failed Smog today 93 wrangler

[Rastamon]

so i took my rig down to the smog only shop and it failed. the emissions test results were:
%CO2 %O2 HC (PPM) CO (%) NO (PPM)
MEAS. MEAS. max / meas. max / meas. max / meas.
15mph 14.3 0.4 89 / 42 .66 / .29 517 / 839
25mph 14.4 0.3 54 / 34 .8 / .25 770 / 790

these are peak measurements only and i failed on the NO (PPM).
the vehicle is a 93 Jeep wrangler; motor is less than 30k, catalytic has less than 50k and the thing hasnt been driven on the street much in the last couple years.
i have replaced the plugs, wires, cap+rotor within the last few months and it runs fine, with the only problem that recently surfaced is that when i am coming off the freeway and to a stop, push in the clutch and the motor dies (although not always; but frequently) other than that the motor runs great. passed the previous smog (2 years ago) with FLYING colors.

my guess is the O2 sensor; the reason being is that the last time it began to stall the way it is now, a new O2 sensor alone fixed it. plus i know for fact that the O2 sensor plays a huge role in how the jeep performs. but would it cause me to fail smog in this particular way?
what other causes could be the problem?
oh, one last thing is that i found a very small hole in my catalytic where it rubbed on the transfercase, and i have not JBwelded it shut yet. could that be the cause?
any help would be greatly appreciated and when i find out what it was, i'll let ya' all know.
thanks!

fawk, my graph looks great in the edit window, but is all fawked in the thread???

[White7]

my rig faild smog and the dude told me to change the oil and bring it back and the fawker passed

[tgariano]

Its dumping fuel, the computer reading lean. When my 4.0 did this it was because the hot wire on the oxygen sensor was grounding out. If you have the three wire o2 sensor look for that (or it can be bad .) The other thing is your cat. isnt working either. Another thing that could cause it is an EGR valve sticken. some times open ,sometimes not when it needed to be.
Just hook a vacuum guage inline with the EGR and enough hose to tape it to the windshield so you can watch as you drive. Should be aroud 12 to 15 lbs when motor running 2k rpm.

[Rastamon]

nice, thanks for the info. i will replace o2 sensor and possibly the cat. i thought it was the EGR too but the smog guy said this vehicle doesnt have one.
prolly retest it next week.

[mbrink]

What size tires do you run? My Scrambler with a 258/4.0 head/Mopar MPI and T18 failed the NOX test at 25 mph. Tried everything to get it to pass, but NOX still high. Changed my tires from 35 to 31's and it passed great. It all has to do with the power band of you motor and the rpm at the test speed. Good Luck.

[Rastamon]

What size tires do you run? My Scrambler with a 258/4.0 head/Mopar MPI and T18 failed the NOX test at 25 mph. Tried everything to get it to pass, but NOX still high. Changed my tires from 35 to 31's and it passed great. It all has to do with the power band of you motor and the rpm at the test speed. Good Luck.

yeah, that sounds about right.. i am running 35" tires right now and i was thinking that same thing when he did the test...fawk! i'm gonna change those before i take it back.
thanks!

[withamc]

If you're not geared for the bigger tires it will hurt your NOX readings. Two times I was able to pass running smaller tires, but the last time even the smaller tires didn't help. New O2 sensor didn't help. New generic fit cat didn't help. BUT... a "stock replacement" cat from Summit did the trick. From what I understand, the fact that the 4.0 does not have EGR puts it all on the cat. If you don't put a 3 way cat designed to reduce NOX emissions it's going to fail.

[juiceman]

Its dumping fuel, the computer reading lean. When my 4.0 did this it was because the hot wire on the oxygen sensor was grounding out. If you have the three wire o2 sensor look for that (or it can be bad .) The other thing is your cat. isnt working either. Another thing that could cause it is an EGR valve sticken. some times open ,sometimes not when it needed to be.
Just hook a vacuum guage inline with the EGR and enough hose to tape it to the windshield so you can watch as you drive. Should be aroud 12 to 15 lbs when motor running 2k rpm.



What are you on, crack? It isn't dumping fuel, the CO is in the optimal range, CO2 looks beautiful, the cat is working the way it is supposed to. I don't know where you came up with dumping fuel.

NOx is caused by high combustion chamber temps, flat out. EGR controls it, when equipped (which it isn't). All other things being equal, I would agree with the other dudes and say take those 35's or whatever off and retest it, it works the engine like a bastard to turn those tires, particularly if you aren't geared, and that alone is likely the cause of failure.

Juice

[DevinB]

Also, a couple easy tricks... If you don't drive it much, especially before you test it, take it on the freeway and get the mph's up. And get a new take of gas with the highest octane. That's all it took to get my '93 YJ to pass the second time around.

[Carlos Garza A.]

Use a propane kit, from IMPCO, in Cerritos California or from Technocarb in Canada... you will get better emissions :flipoff2:

[xjfreak03]

Change your oil. It will take all the hydrocarbons out. Put in a tank full of the good gas. Change the o2 sensor, looks likeyour runnin a bit rich. Have em do a pretest before they do it next time, it'll only cost like $10. That way, if you fail, you haven't just dropped $70 on a smog check.

[Rastamon]

ok, this all sounds good.
the jeep does have 4:56 gears on 35's.
what i will do is replace the O2 sensor, change the oil (its due anyway) i already run the 92 octane and change to smaller tires (for shits and giggles), and the only thing after that it could be is the cat. when i replaced it a couple of years ago i did put in the aftermarket type. so i will price the OEM one out and probably just put it on too, just to be sure.
it is a "smog only" test so the guy cannot pretest it or even mention anything as to what he thinks the problem might be. the shop doesnt have a single tool in it except for the smog machine. smog II sucks even though i am a fan of keeping things clean.

thanks a lot for the help. i'll get back to the thread next week when i take it back for retest.

[NothernAZxj]

SMOG CHECK???????? HMMMM MUST BE SOME CALI THING :flipoff2:


lol hahahahahahahahahaha :p

[whatttup__G]

smog nazi's must die... now that i got that clear :D:D:D


i failed as well with high NO and was told the same thing about high combustion temps... and while the cat is working, a new one will work better, i don't recommend shootin yer wad on teh O2 sensor unless you're sure that its bad again...

for me, i had just done a radiator and t-stat and water pump and it seems the new t-stat runs 10 deg higher than before... i dont know if that makes a huge diff, but i only failed by a little bit... i like the little tire idea, the oil change idea, and then the cat, then maybe a lower t-stat since i seemed to have issues stated above... also, i noticed a small hole drilled in teh pipe ahead of the cat was left open after they got it passed finally.. i know sure as shit i didnt drill it, so it maybe a small dirty trick, i dont know, but he got it passed

best of luck dude

[jeepdude1]

I have a 91 YJ and also failed. my NOX were really high, almost double. I had a low restriction intake, the turbo city one, a high flow throttle body, cam, headers, cat back....you know. One of the things that can cause high NOX is the motor running lean...too much air, not enough fuel. I borrowed a stock air cleaner box and throttle body from a freind, and my jeep passed...barely. Do you have a low restriction intake? Have you removed that cone thing from the intake tube of your box? These might be cheap to check out also. When my jeep passed it was on 37s with 4.56 gears.
Bryan

[mikeswrangler]

also check the exhaust manifold.. it cracks at the two pipes that go in the collector.. mine is right now.. i need to smog mine also this month..

[CanadianTrailblazer]

To bring this topic btt, my '94 YJ with 2.5 just failed its 'smog' test here in southern Ontario, Canada. It is a bone stock automatic YJ with 235-75-15 tires on it and 275,000km. Before the test I did an oil change, plugs and wires, cap and rotor and added some gas line antifreeze. The results are posted below. I was told its totally an EGR problem because only the NOx are high. THIS JEEP DOESN'T HAVE AN EGR SYSTEM. So now what, should I change the cat? I have a stock cat from an '05 Rubicon, if I make it fit will this help. I don't know how to recognize the difference between a 2way and a 3way cat. Can anyone help?

[rocknbronco]

How long did you run this jeep for if you get it good and hot like say 45 minutes to an hour it will burn or atomize the fuel better.I would try that before you give it a go take it out and run some hot laps on the interstae and then take it back see how much better it does.

[raulv240]

You need to lower the combustion temp to lower Nox emissions. Try a cooler range spark plug!

[heeps4ever]

high noX is caused by a high combustion chamber temperature. high temperatures are caused by a lean air/fuel ratio. figure out why its running so lean. ive hear that the 4.0L runs a little lean to begin with, but thats a bit much to fail a smog test. check for a vacuum leak. thats where i would start.

check specs for different cats to figure out which ones are 2-way and 3-way. 3 way cat might have a hose running to it from an air pump system.

[CanadianTrailblazer]

I will pull the plugs this weekend and check their colour to gauge a lean/rich mixture. I never thought of running a cooler plug, I will have to see what I can get. I just replaced them with the original Champions that it called for.

A friend suggested that I tell them its stuck in 4wd so that they could only do a curb idle test. Somehow I don't think they would go for that. Ya think?

[CanadianTrailblazer]

Well, after running a bunch of cleaners (Seafoam, Guaranteed 2 Pass) through the jeep, the NOx went from 1300 to about 960. Too bad 895 is a pass. In frustration, I replaced the cat with a brand new one and NOx dropped to about 200. Passeroo!:bounce2:

[MOB-40]

You Failed Nox, Faulty Causes Either The Cat Or The Egr Valve....

[KiGrind]

So $600 later you pass. :shaking: Is it really worth living in California?

[cjcargo]

I have a 92 XJ with the 4.0L last time I had mine tested it failed! I found the wires to the O2 sensor burned on the exhaust header. Repaired the wires, and retested. It passed with flying colors, and the following time passed again. I only run the 87 octane gas. I have stock gears 3.73 and running 33's. I am putting a new hi pro cat on only because the bracket is rusted out. I always change the oil, spark plugs, and clean the air filter before every test. Ours in Maryland is every two years. Lead foot going to the test helps also! :D

[CanadianTrailblazer]

You Failed Nox, Faulty Causes Either The Cat Or The Egr Valve....
And since a 94YJ with 2.5 doesn't have an EGR system, yes it was the Cat!

So $600 later you pass. :shaking: Is it really worth living in California?
:laughing: Thats funny. The cat was $130 INSTALLED with a receipt and Canda is a loooooooong way from Cali! :flipoff2:

[KiGrind]

And since a 94YJ with 2.5 doesn't have an EGR system, yes it was the Cat!


:laughing: Thats funny. The cat was $130 INSTALLED with a receipt and Canda is a loooooooong way from Cali! :flipoff2:



Too bad I was replying to the thread starter, not the person that derailed it. :flipoff2: I dont even know what the spillway is.

[CanadianTrailblazer]

Ya, the threadstarter hadn't replied since 2004, so I stole his tread. I've never heard of the spillway either, what makes ya think its in Cali?

[KiGrind]

Smog testing (Which is done in my state too just in certain cities.) but it was more of a poke not serious discussion.

[CanadianTrailblazer]

Ya, those losers who live in California with all their sunshine, warm weather and rockin' trails, they suck! They could be living up here with all the snow and ice and muddy granite. Suckas. :p

[PaintedRat]

I still like California, but my Jeep is a 74 (pre-smog), bikes don't have to smog, nor does anything diesel. Down with the smog nazis!

P.S. Tomorrow snow level is supposed to drop to 3000 ft in the Central Valley.

[KiGrind]

I can understand what hte smog nazies are trying to do but I always pictured it a goverment controled thing, you go pick up your licence plate and tags you get a smog check kiund of deal.

Now from the looks of it any po dunk dumbass can build a car port and run smog checks for outragous prices.

[resqme]

I dont even know what the spillway is.

Your loss.

It's the trailhead of the Rubicon, Loon Lake side.

[rocknbronco]

Congrats on the pass