SMOG LEVELS NOx

[corbinafly]

I had the same problem with high NOx earlier this year. Changed all sensors to no avail including the cat. Then I swithed to one step cooler spark plugs and passed. If all else fails, it's worth a shot.

And the PCM does compensate for a lean mixture unless you're at WOT or cold start/warmup which you aren't when testing.

Kyung

 

[RNMedic]

as stated above an exhaust leak will also cause High NOx d/t sucking some air if this is a 4.0 does it have a cracked exhaust manifold?

 

[SPSERG]

I have looked the manifold over, used an inspection mirror too. I cant see or hear any leak. It would have to be a substantial one though right??
Corbina: what were your readings like before and after the plugs? I can swap them out, but have tried 2 sets and very little difference-although the heat range may be no different.

 

[Octane]

Had the same problem with my 95 HO. Was a bad cat. Had it replaced and no more failing grade.

 

[SPSERG]

What year was your Jeep? So, it was a 3-way convertor then?

 

[JEEPZZ]

Since no one else has asked: is the 94 Grand Cherokee in question a 4.0L or a 5.2L V8.
If it's the V8 and has an EGR valve I'd start there and check for proper operation of the valve first.
If it's a 4.0L (no EGR valve), it's more than likely the cat is on it's last leg. As already stated, sometimes a different plug will work if your NOx reading is just outside the limits but in your case I think you'll need a cat.
3 way cats work with an A.I.R. system, something the 4.0L does not have. I'm not sure about the V8. In either case there are replacement universal cats that will work on either style system (the air inlet line just needs to be capped for non-air system).

One last thing to try, high NOx is caused by excessive combustion temps, in extreme cases leading to pre-ignition or detonation. Excessive carbon build up on the piston head is one of the most common culprits. Try a 'carbon blaster' product to try to remove some of the internal deposits. Most professional grade fuel injection cleaner products include some sort of deposit remover.

Most lean running conditions won't cause excessive NOx. An extreme lean condition that induces a misfire will cause the HC's to jump way up along with the NOx reading. Since your HC levels are within spec, I don't believe your problem is caused by a lean running condition or lean misfire.

 

[SPSERG]

Thats resonable, I thought I had mentioned it... Its the 4.0, thats the only reason I brought the question here. Oh, just to update, I replaced the MAP, coolant temp sensor and am waiting on an IAT. Pulled codes, and nothing is stored except the normal code 55. Filled the tank with super, and another can of Seafoam. Does the use of Super have any significant effect on smog output? Dont know if I should rush back to the inspection shop, this time I have to pay. Anything else besides the cat? If I do the CAT, I will do the whole exhaust and I would like to save a few dollars before X-Mas.

 

[AJPulley]

Thats resonable, I thought I had mentioned it... Its the 4.0, thats the only reason I brought the question here. Oh, just to update, I replaced the MAP, coolant temp sensor and am waiting on an IAT. Pulled codes, and nothing is stored except the normal code 55. Filled the tank with super, and another can of Seafoam. Does the use of Super have any significant effect on smog output? Dont know if I should rush back to the inspection shop, this time I have to pay. Anything else besides the cat? If I do the CAT, I will do the whole exhaust and I would like to save a few dollars before X-Mas.

I think you will find a slight improvenment in responce from replacing the cat, especially if it was stock. Don't you have, what, is it 60 days here to get around on the rejection sticker? That will get you into the new year. I have to do mine in January and get safety and emissions. I have a spair TB sitting on the work bench and wanted to get it bored, but have to read up and see if I can find any threads on expected emissions after it's on. You know Mass, I think someone in out DEP is realted to someone in CARB.

I think it's worth a shot to try it again, at least you would know if all the improvements and maintanence did the job. Let me know, would ya?

 

[majic_tech]

My vote is on the cat being bad .....by the way you guys have it easy we have to meet 1.2 co and 220 ppm hc to pass here (no nox testing though) Also those bosch platinums will be a problem im the near future (if they are the standard ones) ive seen them cause excessive misfirirng and take out converters LOTS of times.....(too much hc) what was your hc and co readings when it failed? (co will give you rich/lean clues hc will indicate misfire clues)

 

[JEEPZZ]

by the way you guys have it easy we have to meet 1.2 co and 220 ppm hc to pass here (no nox testing though)

You've got that backwards, your testing procedures are much more relaxed since it does not require the vehicle to be tested under load conditions by use of a dynomometer.
NOx for the most part, is only generated under loaded conditions.
A static rev test does not accurately simulate the conditions we operate our vehicles in during daily use. 1.2 and 220 can quite easily be met with a well running modern vehicle but those numbers can go to crap quickly once load is introduced. Most larger cities and densely populated areas have gone to dyne testing to help reduce NOx's effect with generating photo-chemical smog. Smog is not a big of a concern in less populated areas so it's not tested for in those areas.
An even more strict emissions testing procedure involves plugging directly into the vehicles DLC (data link connector) on OBDII vehicles to retrieve info from the vehicles computer on how the systems are operating, but that's a whole new can of worms.

 

[majic_tech]

You've got that backwards, your testing procedures are much more relaxed since it does not require the vehicle to be tested under load conditions by use of a dynomometer.
NOx for the most part, is only generated under loaded conditions.
A static rev test does not accurately simulate the conditions we operate our vehicles in during daily use. 1.2 and 220 can quite easily be met with a well running modern vehicle but those numbers can go to crap quickly once load is introduced. Most larger cities and densely populated areas have gone to dyne testing to help reduce NOx's effect with generating photo-chemical smog. Smog is not a big of a concern in less populated areas so it's not tested for in those areas.
An even more strict emissions testing procedure involves plugging directly into the vehicles DLC (data link connector) on OBDII vehicles to retrieve info from the vehicles computer on how the systems are operating, but that's a whole new can of worms.

umm ,they do plug into ours and yes ours is a large popultion smog problem everyone, and thier dog, and his trainer, his dog trainers cousin ,his dog trainers cousins migrant no green card packin gardener, and all his migrant worker friends a.k.a illegal aliens,wetbacks .....whatever ,are moving here from california driving up property values and crime ...but thats a whole other can of worms and as an ase certified master tech with an additional advanced engine performance certification and chrysler bronze certification I know what a dlc is as well as how the whole dyno smog thing works...we are going to that in a few years......lovely

 

[PapaPump]

WHOA! all of a sudden this thread went anti-everyone! idaho doesn't have a population problem buddy.

here in northern california we have the same crap with people moving in and driving up property values, if you own a house that's a good thing i suppose.

as far as testing is concerned...population boom or not, more stringent testing is better. i don't care what anyone says about these type of things, cars have only gotten better since 1972. we don't even have very strict standards in this part of the state, but i would like my jeep to pollute as little as possible. unlike most people, i believe efficiency and performance go together.

the only thing i would like to see change is the visual part of the certification. it shouldn't matter if all of the factory equipment is there is the vehicle manages to pass smog. imagine an ls1 swap on an 1982 camaro or something. sure there will be no egr or AIR or whatever else...all the little sensors will be missing, but the engine will be clean and get 25+ mpg. yet because of the way the laws are written, you won't pass visual. i'm sure things could be worked out because the engine is 20 years newer, but they shouldn't have to be. test for emissions, if it pollutes to much it fails, if it is clean, it passes. save the aftermarket from having to carb certify products we all know increase performance and efficiency.

 

[majic_tech]

WHOA! all of a sudden this thread went anti-everyone! idaho doesn't have a population problem buddy.

here in northern california we have the same crap with people moving in and driving up property values, if you own a house that's a good thing i suppose.

as far as testing is concerned...population boom or not, more stringent testing is better. i don't care what anyone says about these type of things, cars have only gotten better since 1972. we don't even have very strict standards in this part of the state, but i would like my jeep to pollute as little as possible. unlike most people, i believe efficiency and performance go together.

the only thing i would like to see change is the visual part of the certification. it shouldn't matter if all of the factory equipment is there is the vehicle manages to pass smog. imagine an ls1 swap on an 1982 camaro or something. sure there will be no egr or AIR or whatever else...all the little sensors will be missing, but the engine will be clean and get 25+ mpg. yet because of the way the laws are written, you won't pass visual. i'm sure things could be worked out because the engine is 20 years newer, but they shouldn't have to be. test for emissions, if it pollutes to much it fails, if it is clean, it passes. save the aftermarket from having to carb certify products we all know increase performance and efficiency.

well if any consolation to ya dude my old renix (87 4.0 m/t) passed THIS MORNING with .09% co and 15 ppm hc is that good enough for you? would you like me to scan the report and post it ???? the point was we do have smog in the treasure valley and unless you live here how could you know that??????I dont have a problem with the testing of any kind...(Im able to get them to pass easily w/o cheating of any kind)....yeah Ive lived in northern cali before (more than one place by the way) and you dont have the bad air quality we do, especially in the winter during an inversion I can tell you that for certain pal......ohh i see earth firster territory eh? IM also doing my part in other ways you know how the vegetarians say not to eat beef because it supports land clearing (to raise cows)and the cows gas is bad for the ozone layer Im doing my part by eating them (the cows, I dont want any further confusion) .................on that note, I conclude with this advise to you kind sir please do your part for pollution control by wearing a condom

 

[yardape]

I had the same problem. Replaced the cat. Passed. the cat was toast.

 

[SPSERG]

I appreciate everyones input. Never did I have the intention of invoking some hard feelings over any states smog testing though. I have exhausted the retest, so the next one we pay for. I was hoping to avoid doing the cat before the holidays, just for the dollar figure involoved. Majic-tech, do you feel that would be a safe way to go? (cat replacement) I REALLY would like to put this Jeep problem behind me

 

[majic_tech]

Well like I asked before what were the hc and co numbers when it failed or do you not have those? I can give you more of a definite answer with those figures....

 

[AJPulley]

Well like I asked before what were the hc and co numbers when it failed or do you not have those? I can give you more of a definite answer with those figures....

Majic-tech, read post #6.

Spserg, I wish you luck. I'd still be curious to know what your problem is when you figure it out. I'd bet the chances are high it'll come down with a cat. Shop around; Maybe someone will have a special on exhaust work. Mine is due January for safety and emmisions. I'll update this with my numbers again when I get it done.

 

[SPSERG]

levels were as follows:
HC 00.37 limit: 2.40
CO 7.60 limit: 60.00
NOx 5.30 limit: 3.00
and 130K on engine
__________________

 

[majic_tech]

Well it doesent have an ignition problem or mechanical shortcoming at all judging by the hc.(but it soon will as i said before bosch standard platinums arent worth a dime , see plug thread)And the co doesent seem excessive if this is loaded on a dyno .I would say the converter is shot. one more question do you have the o2 measurement by chance? If the oxygen content is excessive it also indicates poor converter performance ( it has to use up most of the oxygen in the process of burning off the pollutants) Just went back and read all the thread and Id say with 130000 and what youve already done combined with the gas readings replace the converter and lose the bosch plugs and youll be good to go. And please by all means post your results I have a good reputation to uphold .........

 

[corbinafly]

I have looked the manifold over, used an inspection mirror too. I cant see or hear any leak. It would have to be a substantial one though right??
Corbina: what were your readings like before and after the plugs? I can swap them out, but have tried 2 sets and very little difference-although the heat range may be no different.

Sorry it's taken me so long to respond. I haven't been getting all my email notifications.
Anyways... My NOx reading was 1262 with max allowed of 517.
After the cooler plugs it was 296.

By the way, I first thing I did was change my cat also even though the HC and CO levels were way below average and the NOx actually went up more.

Kyung