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Old 07-25-2014, 12:18 PM   #1
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1990 YJ Failed Emissions in CO - NEED HELP!!!

Hello

I failed with stock equip and carb. I know it is crap but I need it to pass visual here in centennial, CO.

I have done
-Team Rush upgrade- cap, rotor, plugs and wires.
-New O2 sensor
-New air filter
-Oil change

Has small hesitation on acceleration still.

Test info:
HC GPM --- 7.7829 --- limit 3.0000 ==FAIL
CO GPM --- 25.0541 ---limit25.0000==FAIL
CO2 GPM ---456.9379
NOX GPM ---1.5976 ---limit 5.0000==PASS

I was going to run some fuel additive to clean but wanted some other advice
PLEASE any help is welcome

Thx.

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Old 07-25-2014, 01:53 PM   #2
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Have a quality exhaust shop check your cat.
HC is way high, CO is just above.

Usually when you see the 2 together like that, it HAD* a misfire
(*I assume this because you just did a tuneup, and this would repair most misfires), and that killed the cat.

HC is unburnt fuel, also because it is your highest failure, it is your target gas, however an O2 reading could help diagnose the difference between a simple misfire, and a lean misfire (which can cause your elevated CO reading).
Im assuming your timing is set correctly, or you would have posted you had failed for functional timing check.

PLEASE scan the whole report, there is other information on it that helps the diagnostic process.

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Old 07-25-2014, 04:43 PM   #3
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Thank you for the help!

Here is a pic of the doc. There is not too much more info here. The 2nd page is very light and hard to read even on the report. The best I could do.

So your thought is after the tune up it broke the Cat?
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Old 07-25-2014, 08:14 PM   #4
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Another issue I found looking closer. Anyone know what this is and if it would contribute to not passing plus the hesitations misfire when accelerating?
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Old 07-25-2014, 11:26 PM   #5
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OIh yea, Colorado, they dont show O2... darn...

That pipe is for your Pulse Air Injection, those holes could cause high NOx, which unfortunatly is not your problem, however you should get ti fixed.
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http://www.wranglerforum.com/f330/2x...ad-490865.html
'04 SV1000s:
http://www.svrider.com/forum/showthread.php?t=280873
Old Jeep that was totaled (and SOLD!):
http://www.wranglerforum.com/f330/2x...ad-101879.html
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Old 07-26-2014, 01:00 PM   #6
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Thanks 2xs!

I also forgot to note this is a 4.2L
I have not checked the timing so I will do that next.

Few questions:
  • Should I run G2P through a tank and will that help?
  • Is there anything special about the cat for replacement on 1990? Brand?
  • Would you replace exhaust with the cat system at the same time?
  • Would an bad cat cause: Hesitation and almost a stall on acceleration or could this be the misfire?
  • The Pulse Air pipe is that something a shop would need to replace? I am not a welder and have a small garage to work in.

Thanks again for your help 2xs you are awesome!
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Old 07-26-2014, 02:04 PM   #7
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Also on the Plugs I have them gaped at 0.045" with stock canister.
Would it make a difference to put them back to 0.035"?


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Old 07-26-2014, 05:44 PM   #8
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2xs is a smog tech in CA so he knows his stuff. When my 90 4.2 failed repeatedly after tune up, timing, O2 sensor change, etc., I finally took it a guy who knew carbs and had it adjusted to specs. That did the trick. He was actually recommended to me by the last place that failed me.
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Old 07-26-2014, 06:11 PM   #9
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I hate carburetors....

NO GTP, snake oil never really works!
Your local muffler shop should be able to get you the cat you want, or order one from Summit for your exact year make an d model, they wont like it, and wont warranty it, but they will be happy to weld it on for you. They will also probably try to talk you into stuff you dont need, just make sure there are NO holes int he exhaust, espically before the cat (like that Pulse air tube) and yes, they can weld that up for you....

A plugged up can can cause a hesitation, and a top end loss of power (think restriction).
BUT, the hesitation is probably due to your carb, have a guy good with carbs look at it, he will know best.
Remember, I hate carburetors, so.... Ill try to talk you into an EFI swap kit....

http://howellefi.com/tbi-kit-1972-80...ons-legal.html
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'93 Black YJ, 4.0L AX15 - UNDER CONSTRUCTION!
http://www.wranglerforum.com/f330/2x...ad-490865.html
'04 SV1000s:
http://www.svrider.com/forum/showthread.php?t=280873
Old Jeep that was totaled (and SOLD!):
http://www.wranglerforum.com/f330/2x...ad-101879.html
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Old 07-26-2014, 08:04 PM   #10
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Quote:
Originally Posted by 2xs View Post
I hate carburetors.... NO GTP, snake oil never really works! Your local muffler shop should be able to get you the cat you want, or order one from Summit for your exact year make an d model, they wont like it, and wont warranty it, but they will be happy to weld it on for you. They will also probably try to talk you into stuff you dont need, just make sure there are NO holes int he exhaust, espically before the cat (like that Pulse air tube) and yes, they can weld that up for you.... A plugged up can can cause a hesitation, and a top end loss of power (think restriction). BUT, the hesitation is probably due to your carb, have a guy good with carbs look at it, he will know best. Remember, I hate carburetors, so.... Ill try to talk you into an EFI swap kit.... http://howellefi.com/tbi-kit-1972-80...ons-legal.html
For $1300 I can live with the Carter carb.
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Old 07-26-2014, 08:16 PM   #11
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Thanks!

Monday I will talk with a muffler shop and see what my options are. Any idea what a new cat should cost?

I have been told to do the motercraft carb upgrade but am worried I will not pass here in Denver with visual. I don't know all the requirements for visual here. Seems like if a better carb and it still passes the smog test it would be legal.

I have heard a lot about the Fuel injected but man that is pricy.

Thanks again 2xs your info is very helpful. I will try to post an update.
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Old 07-26-2014, 08:52 PM   #12
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I put a new cat and Flowmaster exhaust on mine 2years ago, I think it was about $300
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Old 07-31-2014, 02:34 PM   #13
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Thanks 2xs!

I put a new CAT and fixed the Pulse Air Injection. The carb was shot PO must have had a fire because parts were burnt up. Accelerator pump replaced and timing adjusted.

PASSED flying colors!

Thanks again for all your help and suggestions.


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