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CA SMOG, HIGH NOx

I went through all the schooling for CARB/Smog and was ASE certified in 8 areas.

I don't have a problem with Bosch. The NTK I put in there 2 years ago crapped out.

Yesterday I found a small crack in my down pipe and it wasn't tight up against the doughnut. Welded the crack and tightened it up the exhaust manifold. I pulled the plugs and looked down at the top of the piston and there is a massive amount of carbon build up. Going to Seafoam today. I removed the new plugs and catalytic converter and installed a test pipe and the old plugs set to .035. Going to a 180 thermostat and some Water Wetter. Then of course change the oil. Going to test the CTS and the AIT in a controlled setting (pan of water) too.
 
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I've been using a Bosch O2 sensor on my 1995, and previously used one on my 1991. The only problem I've seen was a cracked header on the 1991 causing high Nox. I replaced it with a Borla and it's been fine ever since. That system is on the 1995 now and it passed easily. I just drive it over to the smog place and hand them the keys. 87 octane in the tank, change the oil once a year. The jeep isn't a DD, and I do believe my cat off the 1991 pre-dates the whole CA cat on everything they implemented in 2010 or so. It's a generic walker 2.5" in/out cat.
 
Well I took the Jeep in to get smogged again cold, figured perhaps it would pass while running in rich cold mode. No dice, It failed with miserably high NOX.

I rigged up a MAP sensor voltage regular to up it to 5.5V reference from the original 5V in hopes it would richen up the cycle when warm. Again no dice, failed miserably to even higher NOX, higher than 1000+ppm. I found this result to be really odd...

As i was about to leave, the smog tech from a few years ago showed up and recognized me, he disconnected my coolant temp sensor and she passed with flying colors. I am again amazed, i would love to really solve this problem or figure out what really is happening here !!!

Pete

 
Smoked the neighborhood using the Seafoam.

Found the cracked exhaust manifold everyone speaks of. Putting Thermosteel/Quicksteel on it as a Bandaid fix to pass smog. I have an APN header I'll be putting on next week or so.

Tested the CTS and it passed. Less than 1000 ohms at operating temperature.

Tested the thermostat and it failed. At 212 it still didn't crack open a bit. Installed the new thermostat I bought yesterday.
 
Jeepsrock... cool it passed smog this round by once again disconnecting the cts. Unfortunately not doing any good in the long run and hopefully the smog guy doesnt get a visit from the state for your car lol. Post your failure VIR as well to see how lambda comes out... at this point being that this is strictly a major nox issue regardless is the mixture is rich or not its time to do an intrusive exhaust test on the dyno and to smoke the exhaust pre catalyst to check for tiny leaks. This is a typical 5 gas reading when your engine is in perfect tune but any exhaust leak WILL render the nox reduction bed useless. Oh and did I already talk about the need for a good o2 sensor as well you would be so so suprised.

Cat
Exhaust leaks
Good o2 sensor

This is the only possible areas of fault at this time for you. My readings from passing smog was below 100ppm nox.
 
Brought to have a diagnostics done on it. They welded up a small hole in the new catalytic converter and replaced the MAP sensor as it was lazy. Persistence and cash can fix anything.

 
I would replace the CTS then.

jeepsrock said:
Well I took the Jeep in to get smogged again cold, figured perhaps it would pass while running in rich cold mode. No dice, It failed with miserably high NOX.

I rigged up a MAP sensor voltage regular to up it to 5.5V reference from the original 5V in hopes it would richen up the cycle when warm. Again no dice, failed miserably to even higher NOX, higher than 1000+ppm. I found this result to be really odd...

As i was about to leave, the smog tech from a few years ago showed up and recognized me, he disconnected my coolant temp sensor and she passed with flying colors. I am again amazed, i would love to really solve this problem or figure out what really is happening here !!!

Pete

Click to expand...
 
AWESOME numbers, congrats.

Locked98GC said:
Brought to have a diagnostics done on it. They welded up a small hole in the new catalytic converter and replaced the MAP sensor as it was lazy. Persistence and cash can fix anything.

Click to expand...
 
I have a 1994 Jeep Cherokee, 4.0L, Automatic.
He disconnected the coolant temp sensor? Really. I've been struggling with my Jeep too. Same results basically. High NOx and gets worse each time. You disconnected the temp sensor?
Anything else ? I'm doing tests on my O2 sensors now. Had 3 different ones. Had issues with a new Catalytic converter put in. Then found cracked exhaust manifold. replace manifold. Failed still. Swapped O2 sensor. Failed. Ran cleaners, seafoam etc. Failed . Similar to yours. Please help me ! I've had my Jeep sidelined now for a year because of this mess. Had other things to deal with too in my DD. HELP please.
======================
Should I post new thread?
 
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That dent is there from the factory for driveshaft clearance.
I've read posts from, I think, a Jeep dealer tech who claimed that only the very best o2 sensors for these Jeeps had a fast enough slew rate to keep emissions happy. Worth a shot, maybe.
Any air leaks will do some harm, too.
Also : disconnecting the coolant temp sensor will put the computer into open loop, where it defaults to running slightly rich to protect the engine - which should cool combustion temps a bit. I've heard of it working for nox emissions.
Most smog techs won't allow it through with a disconnected sensor but you might be able to get into the harness & hide another connector, so it's plugged in at the harness but not to the computer...
 
That dent is really a dent? So I thought. I'll post it later.
I understand that NGK and NTK are the same? Same company. NTK is NGK's other name for the sensor? Per Napa, NGK O2 sensor:

http://www.napaonline.com/Catalog/C...ensor-OE-Manufacturer/_/R-NGK23023_0295704028

I have a smog shop that I paid for unlimited testing. Then for final setup, I pay that smog rate. So far, 4 runs and big fat fail every time. Everything was better when had the cracked exhaust manifold. Really weird. I'm going to run the pretest again later this week so I have a baseline. If it fails, I'll ask to run it with the coolant sensor unplugged. I'll do that harness connection thing to check it. I'm sure I could get it doing the test without it connected but I don't want to put the shop in that position. I'll do the false connection and see what the results are.

I'm paying attention to that clean out the coolant system./ Mine is rather old, dirty. Is the Best way is to drain it? Then flush thru with a garden hose from the top?
 
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Wow guys, I have a 1994 4.0 HO ZJ but I have been suffering the same smog issues as jeepsrock. I am bald from pulling my hair out over this, but I refuse to give up!

My lambda is showing slightly rich, numbers are good except for NOx. Ive changed the cat twice, 3 times including the newish one that was already on it when it failed.

Barely passed in 2012, BARELY after lots of trial and error but the issue is back.

I do have a WJ manifold swapped in, but It passed in 2010 with this manifold and stock injectors. Failed in 2012. Failed in 2014.

I also have a FIPK. Tested with it..failed. tested without it..failed.

I have replaced:

plugs, put in champions, gapped to .35

o2 sensor (bosch...I know.. I have a NTK on order, should be here tomorrow)

New exhaust from headers to tailpipe. Stock failed, put in Kolak 2.5" with Magnaflow high flow cat...failed.

The entire exhaust front to back was put in professionally by a very reputable exhaust shop. I went with General Muffler in Orange. They used to weld up headers for mopar. I know the exhaust isnt leaking with very good certainty.

changed cap/rotor/wires

Stock 1994 OEM injectors cause a fail high NOx, installed brand new flow matched injectors dodge neon 703 injectors failed. tried WJ 2004 injectors..failed.

New fuel pressure regulator. Fuel pressure is within correct specifications.

I have also seafoamed. No change. I did a steam cleaning, no change, failed.

I had a 63mm throttle body. failed. put on stock..TB failed. ARRGGGGHHH!!!!


Took spark plugs out and looked at piston tops. Dont look too bad, gently scraped piston tops, they were pretty clean.


I DONT KNOW WHAT ELSE TO DO! I dont want to pass this thing with BS measures. I want it fixed and to not kick the can down the road like I did in 2012.

I dont know what else to try. At this time, after reading all 8 pages on here I am HOPING LIKE HELL it is the o2 sensor. I have a brand new bosch installed, it has under 2000 miles. After much research today I ordered a NTK. I HOPE HOPE HOPE that is it.

Ive posted on JF with this issue, much more in depth, but I am impressed with the support in this thread.

You guys rock!

Here is my numbers in 2012. They are the same now, if not a little worse. THe smog tech ran it in manual mode this year so I dont have a printout. NOx was going 800-1000.

Every time I have mentioned failed smog tests above, HC, CO CO2 Oxygen always almost identical, each time I tested I failed with high NOx. Everything else is within spec.

IMG_20120518_200942.jpg
 
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What about radiator , fan clutch , water pump, thermostat? High nox can be high combustion temps? Did you advance the timing at all with the CPs? Coolant temp sensor? Clean all grounds?
 
OK, there comes a time to wave the white flag. If the new O2 sensor doesn't do it, consider taking it somewhere really, really good. At he risk of sounding like an advertisement, I'll recommend the one my non-smog mechanic recommended to me for really tough problems. Mind I don't know the people there, and I've only been there once myself - but they solved a stubborn smog problem for me in about 30 minutes. It was worth the drive. The guy there had the highest score ever recorded on the technician's exam (admittedly awhile back), and he teaches smog refresher courses throughout the year. You're listed in L.A., but as you have had work done in Orange, it might be worth it to head out a little further to Hemet, CA. Try http://philsautoonline.com/ (Phil's Auto Clinic). Best of luck.
 
JoCat said:
OK, there comes a time to wave the white flag. If the new O2 sensor doesn't do it, consider taking it somewhere really, really good. At he risk of sounding like an advertisement, I'll recommend the one my non-smog mechanic recommended to me for really tough problems. Mind I don't know the people there, and I've only been there once myself - but they solved a stubborn smog problem for me in about 30 minutes. It was worth the drive. The guy there had the highest score ever recorded on the technician's exam (admittedly awhile back), and he teaches smog refresher courses throughout the year. You're listed in L.A., but as you have had work done in Orange, it might be worth it to head out a little further to Hemet, CA. Try http://philsautoonline.com/ (Phil's Auto Clinic). Best of luck.
Click to expand...

anything like this in sacramento, CA ? hahaha. I have a bad feeling about mine this year...
 
JoCat said:
OK, there comes a time to wave the white flag. If the new O2 sensor doesn't do it, consider taking it somewhere really, really good. At he risk of sounding like an advertisement, I'll recommend the one my non-smog mechanic recommended to me for really tough problems. Mind I don't know the people there, and I've only been there once myself - but they solved a stubborn smog problem for me in about 30 minutes. It was worth the drive. The guy there had the highest score ever recorded on the technician's exam (admittedly awhile back), and he teaches smog refresher courses throughout the year. You're listed in L.A., but as you have had work done in Orange, it might be worth it to head out a little further to Hemet, CA. Try http://philsautoonline.com/ (Phil's Auto Clinic). Best of luck.
Click to expand...

Thanks for the recommendation. I will have to check him out if this doesnt work.

Does anyone here think the WJ manifold might be causing my issues?
 
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