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  #181  
Old January 21st, 2017, 09:47
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Re: CA SMOG, HIGH NOx

I have never believed the local folklore here that NTK O2 sensors are way better than Bosch. The Renix sensor was invented and was OEM from Bosch. That is what I use. All my rigs are Renix, and most here say NTK is best for the HO rigs. The real story is to pull out an analog volt meter and test the dam things with an O2 bottle, and flame from a torch, and to test the wiring internals for about 8 ohms on the internal resistance wire heater, and test for the voltage to the sensor and to sensors heater... test the ground and so on.

Is your rig Renix or HO? Year?

This could be a good lesson for everyone having NOx smog test issues!!! It is called bias, and it is hard to test for with out a CO2 and O2 feed bottle and flow measurement meters to run the O2 concentration up and down in a quantifiable way. May be a good thread idea folks!!!! Bottles are cheap, just need good lab flow meters.

Congrats on saving the jeep and fixing your problem. Took me years to solve of my never seen before, Renix sensor problems, LOL.



Quote:
Originally Posted by snooop1e View Post
SOLVED!!! I PASSED!!!

I replaced the BRAND NEW OEM NTK oxygen sensor with a BOSCH oxygen sensor and dropped Nox from 1600 and 1500 to 10 and 0.

Which means I spent over $900.00 and approx 40 hours working on my Jeep, missed several days of.work and failed 5 smog tests simply because a BRAND NEW NTK oxygen sensor was sending bad data to the computer indicating a rich AFR so the computer leaned out the AFR Thanks NTK!
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  #182  
Old January 22nd, 2017, 13:09
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Re: CA SMOG, HIGH NOx

Quote:
Originally Posted by snooop1e View Post
SOLVED!!! I PASSED!!!

I replaced the BRAND NEW OEM NTK oxygen sensor with a BOSCH oxygen sensor and dropped Nox from 1600 and 1500 to 10 and 0.

Which means I spent over $900.00 and approx 40 hours working on my Jeep, missed several days of.work and failed 5 smog tests simply because a BRAND NEW NTK oxygen sensor was sending bad data to the computer indicating a rich AFR so the computer leaned out the AFR Thanks NTK!

When I switched my '91 XJ dash board from idiot lights to the xj gauge cluster, I installed an NTK temp sender (on the back of the engine head, driver's side). It was totally off. I replaced it with a genuine mopar, and it worked beautifully. I also have a Bosch O2 sensor, and it's always worked well.
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  #183  
Old January 26th, 2018, 22:26
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Re: CA SMOG, HIGH NOx

Here we are again and its time to get the Jeep smogged. If you follow the thread from the beginning you'll see that every other year since 2012, no matter what i did i always ended up having to unplug the CTS sensor to get the Jeep to pass smog with decent NOX values

This time instead of wasting time for what could not have been fixed over several years i want to have a better idea of what actually happens when the CTS is disconnected ?

Does it assume max resistance value and thus extra cold causing it to richen the mix ? Or does it realize there is no sensor (due to the infinite resistance) and use a predetermined value, if so what is that value ?

Thanks,
Pete
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  #184  
Old January 27th, 2018, 08:22
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Re: CA SMOG, HIGH NOx

Is it an HO, OBD-1 or II or Renix? What year?

Old_Man proved that a bad CTS on his Renix made it run rich, kept it from ever reaching closed loop operation, it drank gas all the time. Your test Data is wrong for an engine running rich and running in open loop, it is the opposite.

Has the CTS been tested at 0*F and and 212 F in ice water and water boiling water to see it meets OEM specs? Was it replaced with a tested CTS??? Is the CTS telling the computer the coolant is hotter than it really is?

Is the CTS wiring shorted, or making the engine run too lean?

Are the CTS e-connectors clean and tight?

Is the CTS ground wire reading less than 1 ohm to the battery negative post (Renix rigs)
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  #185  
Old January 27th, 2018, 09:48
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CA SMOG, HIGH NOx

It's a 94 HO OBDI Jeep XJ

My question is a bit different, I am asking what does the computer assume when the CTS is disconnected?

Pete



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  #186  
Old January 27th, 2018, 12:17
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Re: CA SMOG, HIGH NOx

Quote:
Originally Posted by jeepsrock View Post
It's a 94 HO OBDI Jeep XJ

My question is a bit different, I am asking what does the computer assume when the CTS is disconnected?

Pete



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I will repeat, it assumes the engine is very cold, to protect the engine from running too lean and burning up the engine, and so it runs the engine super rich. Your test data was lean, not rich, so my guess is that when you disconnected it, there must be a short in the two CTS wires in the harness telling the computer the engine is warm or hot, enough for it to go closed loop anyway.
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34 MPG , '85 2WD Cherokee Pioneer with custom installed, 64 hp, 2.2 L Nissan SD22 Diesel 5 spd Manual; & 4 Renix XJs, '87 Wagoneer 4.0, 4WD, 89-Cherokee, 4WD, '87 Cherokee 2WD, & '89 Cherokee Pioneer 2WD, all 4dr. #2091
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  #187  
Old January 27th, 2018, 12:22
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Re: CA SMOG, HIGH NOx

Quote:
Originally Posted by Ecomike View Post
I will repeat, it assumes the engine is very cold, to protect the engine from running too lean and burning up the engine, and so it runs the engine super rich. Your test data was lean, not rich, so my guess is that when you disconnected it, there must be a short in the two CTS wires in the harness telling the computer the engine is warm or hot, enough for it to go closed loop anyway.
Yes I'm definitely running lean, no doubt about that..

When the CTS is disconnected, it immediately throws a check engine lamp. To me this means that the computer is able to differentiate between extremely cold temperature (-40deg) the sensors max cold read and complete disconnected state.

If there was a short in the harness then no matter connected or disconnected it would result in a very small resistance thru the short... Is my thinking along the right lines or no?

Thanks,
Pete


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  #188  
Old January 27th, 2018, 14:52
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Re: CA SMOG, HIGH NOx

OK, now I am confused, I thought you said you disconnected the CTS and passed emissions doing that last time? How is that possible if it throws a code when you disconnect it???

You can test the CTS with an ohm meter and temp gauge at 3-4 temps to see if it is accurate. If it is not, it could be biasing the ECU timing a bit. But running lean usually means too little fuel and low fuel pressure, or dirty injector(s).

Sounds like the harness is ok, yes!!! One down!!
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Quote=8Mud: "Go ahead and put up the best fence you can build, I'll bet on some Mexican with a few dollars of nails and a pile of scrap lumber."
34 MPG , '85 2WD Cherokee Pioneer with custom installed, 64 hp, 2.2 L Nissan SD22 Diesel 5 spd Manual; & 4 Renix XJs, '87 Wagoneer 4.0, 4WD, 89-Cherokee, 4WD, '87 Cherokee 2WD, & '89 Cherokee Pioneer 2WD, all 4dr. #2091

Last edited by Ecomike; January 27th, 2018 at 14:57.
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  #189  
Old January 27th, 2018, 14:55
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Re: CA SMOG, HIGH NOx

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Originally Posted by Ecomike View Post
OK, now I am confused, I thought you said you disconnected the CTS and passed emissions doing that last time? How is that possible if it throws a code when you disconnect it???
Let's just say the check engine light wasn't seen...

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  #190  
Old January 27th, 2018, 15:11
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Re: CA SMOG, HIGH NOx

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Originally Posted by jeepsrock View Post
Let's just say the check engine light wasn't seen...

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Have you replaced the CTS with a know to be good, tested and proven to be accurate CTS????
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Quote=8Mud: "Go ahead and put up the best fence you can build, I'll bet on some Mexican with a few dollars of nails and a pile of scrap lumber."
34 MPG , '85 2WD Cherokee Pioneer with custom installed, 64 hp, 2.2 L Nissan SD22 Diesel 5 spd Manual; & 4 Renix XJs, '87 Wagoneer 4.0, 4WD, 89-Cherokee, 4WD, '87 Cherokee 2WD, & '89 Cherokee Pioneer 2WD, all 4dr. #2091
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  #191  
Old January 28th, 2018, 12:31
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CA SMOG, HIGH NOx

Tested the IAT and the CTS externally, values look right on both cold and warm.

Took it to the smog tech to run it manually and get some general NOX values to know where we are, 700+

Anyone locally here want to have a whack at it or know someone who would.... Perhaps it's timing related?

Pete


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  #192  
Old January 29th, 2018, 13:16
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Re: CA SMOG, HIGH NOx

Something that might be worth noting here...

The Jeep starts right up when its cold, but when its warm it takes some cranking to get it started and when it starts it isn't very smooth for a few seconds ?

Pete
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  #193  
Old January 29th, 2018, 13:33
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Re: CA SMOG, HIGH NOx

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Originally Posted by jeepsrock View Post
Something that might be worth noting here...

The Jeep starts right up when its cold, but when its warm it takes some cranking to get it started and when it starts it isn't very smooth for a few seconds ?

Pete
Sounds like a bad IAT Intake air temp sensor, but a loose ground or sensor connection can be temp sensitive. Have you tested the IAT and MAP sensor with a calibrated vacuum test rig, temp sensor and Volt/Ohms meter per the FSM???


If the IAT is bad, you may have biased the computer calculations with the disconnected CTS and thus solve the lean issues while the CTS as off line???
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34 MPG , '85 2WD Cherokee Pioneer with custom installed, 64 hp, 2.2 L Nissan SD22 Diesel 5 spd Manual; & 4 Renix XJs, '87 Wagoneer 4.0, 4WD, 89-Cherokee, 4WD, '87 Cherokee 2WD, & '89 Cherokee Pioneer 2WD, all 4dr. #2091
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  #194  
Old January 29th, 2018, 13:44
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Re: CA SMOG, HIGH NOx

Quote:
Originally Posted by Ecomike View Post
Sounds like a bad IAT Intake air temp sensor, but a loose ground or sensor connection can be temp sensitive. Have you tested the IAT and MAP sensor with a calibrated vacuum test rig, temp sensor and Volt/Ohms meter per the FSM???


If the IAT is bad, you may have biased the computer calculations with the disconnected CTS and thus solve the lean issues while the CTS as off line???
Take a look..

Pete


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  #195  
Old January 29th, 2018, 15:11
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Re: CA SMOG, HIGH NOx

Quote:
Originally Posted by jeepsrock View Post
Well I am an Engineer and have a Oscilloscope, so I wouldn't mind taking the time and monitoring the O2 sensor output if it helps me get some useful information, is there some procedure?

Also, does anyone have a good guide on how to check the MAP sensor, all the ones I've seen haven't included data to check at different points weather it be various RPMs and or conditions?

Thanks
Pete
You test it with a hand vacuum apply to the vacuum nipple, and pull various stable vacuums amounts on it and test the resistance, or the live voltage output, against the Factory FSM data table.

Is the O2 sensor new, with no change in the problem, is it Mopar or what brand?

Have you run a compression test, and rechecked the spark plugs since a year ago, for any difference in color or fouling, and thus a possible lean or rich cylinder clue throwing the O2 sensor off balance? All it takes is one lean cylinder, cause by the other(s) being rich, or caused by a partly clogged injector making one cylinder too lean.

Are there any, ANY other operating issues at all, or anomalies???
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34 MPG , '85 2WD Cherokee Pioneer with custom installed, 64 hp, 2.2 L Nissan SD22 Diesel 5 spd Manual; & 4 Renix XJs, '87 Wagoneer 4.0, 4WD, 89-Cherokee, 4WD, '87 Cherokee 2WD, & '89 Cherokee Pioneer 2WD, all 4dr. #2091
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