93 YJ Failed Smog - Need Help and Suggestions

Hi all,
YJ failed smog this morning and if anyone can point me in the right direction as to what to check first, I'd greatly appreciate it..
Looks like hydrocarbons measured at 95 PPM (max allowable is 89)
NO measured at 592 PPM (max allowable is 517)
CO2 is good at .4% and CO is good at .27% (max on CO is .66%).
Something else I just noticed on the print-out, but don't know if it makes any different.. NO failed at 15 MPH but passed at 25 MPH..
Thanks for all your help, everyone..
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What I do is make sure all normal maintenance is up to date, it's surprising how much clean oil will help, and of course the filers. An '93 should be on it's forth set of spark plugs, so make sure they're fresh along with their cap, rotor and wires. Your thermostat has probably been replaced over this period, make sure it's 195 degree one for your SMOG computer to reach normal operating mixture. Of course there can't be any exhaust leaks, maybe you should go ahead and replace the catalytic converter that's it's job to convert hydrocarbons, nitrogen oxides, and carbon monoxide into harmless water and nitrogen. My Bronco with over three hundred thousand miles:
http://www.billhughes.com/smog.jpg
God Bless America, ßill O|||||||O mailto: snipped-for-privacy@aol.com Saigoncal1 wrote:

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I had very similar results when I took my 94 YJ through early last year. It seemed to run just fine and just had plugs, rotor, cap, wires replaced. I took it to a few shops that needless to say I will never use again that didn't fix the problem. Finally found a shop that pin-pointed the problem - bad cat and broken exhaust manifold bolt that I sure as heck couldn't spot looking around at everything (the head of the bolt was still rusted on to the manifold so it looked kosher at casual glance.) Be careful out there of anyone wanting to do anything radical, esp. if it seems to run good.
-jd

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any
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I will second the opinion on the catalytic converter. All of the numbers seem pretty close to baseline, except for the CO2, which ought to be a lot higher than that if your catalyst is functioning. Replace the cat.
Jerry

makes
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Thanks everybody for your input.. I tuned the jeep up over the summer but it's been almost a year since the last oil change so I'll take care of those things and check out the catalytic converter.. the jeep is a pretty strong-running beast so it should be okay.. never loved a car before..

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Here's a question for you - is this '93 manual or automatic? I had a similar problem four months ago (I failed) - and mine's automatic, so I put in a new cat converter (numbers went up), changed the O2 sensor, no improvement at low speed test. The shop that finally got a passing reading said that they had to get the tranny into third gear for a minute, then they tested at low speed and the Jeep passed the low speed test without any problem, then passed the high speed test, by the book. Go figure. I'd never heard of anything like this, but the shop has NASCAR and NHRA certs (they actually compete), and they know their stuff. FWIW...
Regards,
Doug GAvilanes Garden Grove, CA.
Saigoncal1 wrote:

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It's a manual.. I hate automatics.. :)
Hey guys, my Chitlins manual is telling me to take the jeep into the shop to change the cat and won't give me directions on how to do it myself.. I may just tune the beast up and change the oil and then try to smog it again, but if that doesn't work then I probably want to try changing the cat myself before giving it over to a mechanic, which I haven't got and am not sure which local mechanic to trust with my jeep if it comes to that..
Anyway.. anyone know where I can find catalytic converter installation instructions for a 93 YJ?
Thanks again everyone..

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On 24 Feb 2004 17:23:13 GMT, snipped-for-privacy@aol.comspamoff (Saigoncal1) wrote:

It isn't hard. Take your torch, cut the old one off, then weld the new one in it's place.
-- Old Crow '82 Shovelhead FLT 92" 'Pearl' '95 Jeep YJ Rio Grande ASE Certified Master Auto Tech + L1 TOMKAT, BS#133, SENS, MAMBM, DOF#51
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