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High NOx, can't pass CA smog

yeah, in most cases I probably would have taken it to pepboys just to see what they said or just gone with a NAPA cal cat which has passed it the last two times. But being that I just paid for a new cat (I got a discount at Kragen, even though I swore last time I was only using NAPA), I didn't want to rebuy a part.

With regards to the sensors, well, it was all planned to do eventually....I figured I wanted all new sensors in a new engine....hell, wanted to do the Hesco wiring kit too, just didn't have the funds at the time. (old engine had an engine fire and many of the old sensors continued to work but had suffered some damage)

I also kinda figured a lot of the 50 state mods might be fine alone, but when you start popping them all together (injectors, air filter, header, cat back, hi flow cat, etc.), they have to have some sort of chain reaction....one of the reasons I generally stay away from hi-flow cats....but I thought with a brand new rebuilt engine, I was gonna be safe.

As for the injectors, yes, they were reconditioned, but they came with flow specs from Precision Auto Injectors, and they were all dead on. I have wondered if the multi-port injector vs. the single port injector that comes stock might also have something to do with it, generating a finer mist and consequentially a more efficient and hotter explosion.

And yes, the new engine did get new freeze plugs, but I saw the engine while it was being build, and happen to admire the new freeze plugs as I had rusted a few of my old ones out and it was a concern....they all looked to be completely flush, so I don't think coolant interference/restriction is an issue.

Sealing up the exhaust hole made a huge difference....and I'm curious if I need to run some seafoam through the intake to find any other potential leaks. I did check the torque on the exhaust/intake manifold and it was dead on.

Don't think I mentioned, either, I checked my oil, which is only about 1500 miles, but maybe 3-4 months old, and it was black as coal....it was also about a 1/2 quart too full. Freaked me out at first, I saw bubbles and thought a head gasket blew, until I realized it was just air bubbles. But hoping a new oil change with correct level and a new filter will help stabilize it too.

And I wish I could pull, or short the temp sensor, but that's gonna throw a CEL, I tried, and that in itself will fail the visual test. =(
 
So I got to thinking, and starting putting common threads together....

Jeeps tend to fail smog on NO...

Vehicle run at low RPM during smog tests...

Jeeps tend to overheat in traffice, often caused by failing fan clutch....

Maybe I drank too much this afternoon, but I'm starting to think the low rpm and overheating might be more related to a crappy cooling system....I know it's not vacuum tight because the stupid plastic switch thingy leaks like a seive.

Starting to think eliminating the heater bypass and setting up an all electric fan system might just be the way to go.
 
it's on 33x12.5x15. And unfortunately, that is the smallest tire I have. We did inflate the tires from 32 to 45 and that brought the numbers down from 800 to the 755.

Anywho, we'll see. Shop just opened up and they're supposed to be running a "lukewarm" test on it this morning.
 
cool. interesting though. i allways thought getting the cat as hot as possible was the way to pass smog.
 
In a sense yes...the theory behind this times relies more on timing.

A new catalytic converter will heat up rather quickly, he said, generally in the neighborhood of 3-5 minutes. The engine, on the other hand, takes closer to 7 minutes to warm up, and that gives him a couple minute window of when the cat is hot enough to filter the HC and CO, but the engine block is still cool enough that there isn't any NO being produced yet.

If he gets it timed correctly, it's almost impossible for a vehicle to fail.

I don't want to advertise his name on the net, but if you're in the san diego area, and you want a trustworthy "Test Only" spot, shoot me a tell and point you in his direction.

He is the only legitimate "No pass, no pay" shop I've ever run across....usually there is some kind of gimmick, not at this guys shop. He charges a bit more, but IMHO, well worth it!
 
Numbers from the "lukewarm" test...

SMOG-5-2-12.jpg
 
I just had an epic battle with the dreaded high nox, after tinkering with everything I finally passed, I wanted to post what actually worked for me!

Assuming you Cat is good, no Vacuum leaks or Exhaust leaks, your o2 and other sensors are good this is what will work, or at least worked for me!

I replaced the spark plugs with a colder heat range, Champion RC9YC spark plugs. I also flushed the cooling system and installed a 180* thermostat.

It took my 15mp nox reading from 800-900 in previous tests to 250ppm, my research told me that high nox was caused by excessive combustion temps, and thats what i did to fix it!

Hope it helps!
 
So I now have this jeep and its failing smog again! I have to test it at a star smog shop (they are a pain in the a**) When I got the jeep it was running cold so I replaced the t-stat, fan clutch, both temp sensors and coolant. I sea foamed, did an oil change and ran fuel injector cleaner in a tank of gas.

I ran 91 and fuel octane booster. I drove the jeep for 30 mins before getting to the shop but had to wait an hour for the tech to finish lunch. Heres the numbers I got.

f0f06c2d-3003-43a6-b2af-a39307e2c964_zpsc1c2d3cf.jpg


The smog tech said with the jeep being .30 over its always going to have smog issues, Is this true? Would getting a bored out throttle body help at all?
 
Great thread! I failed smog today with high NOx, but now I have several ideas to try before the retest, including borrowing the wheels and tires off my GF's stock rig.
 
Yep. Read that!

I'll give it a try after I replace the fuel filter, swap out the tires, and check for exhaust leaks. Thanks for the tip!

I replaced the spark plugs with a colder heat range, Champion RC9YC spark plugs. I also flushed the cooling system and installed a 180* thermostat.
 
I tried the tire trick, made no difference.

I actually got the idea for the colder plugs from a random thread on a Import Car forum that talked about excessive combinations temps.

I failed 3 times trying different tricks I read on here and cherokee forum, the colder plugs in conjunction with the cooler thermostat made all the difference in the world.

Good luck bro
 
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