jeepsrock
NAXJA Forum User
- Location
- LA California
How do i check for that ?
Pete
Pete
CA SMOG, HIGH NOx
- Thread starter jeepsrock
- Start date
Ecomike
NAXJA# 2091
- Location
- MilkyWay Galaxy
jeepsrock
NAXJA Forum User
- Location
- LA California
I used the shop vac to check for any exhaust leaks over the weekend, found a tiny pinhole leak between the cat and the muffler.. I think since I only have one oxygen sensor that shouldn't affect anything right?
I also tested all the vacuum hoses and found no leaks at all :/
I'll check the distributor and coolant temp sensor next..
Pete
Sent from my Moto G (4) using Tapatalk
I also tested all the vacuum hoses and found no leaks at all :/
I'll check the distributor and coolant temp sensor next..
Pete
Sent from my Moto G (4) using Tapatalk
Ecomike
NAXJA# 2091
- Location
- MilkyWay Galaxy
Have you tried running gumout or a similar product through it to clean out the carbon deposits that can cause high NOx?
Also have you tried a new, high quality Cat converter. They are dual function. They use the rich excess fuel to heat the first catalyst as the excess fuel is consumed, which then activates the NOx catalyst to destroy the NOx and the hydrocarbons catalyst to destroy the hydrocarbons.
Also beware that poor electrical sensor contacts can through off the ECU readings and operations, it is called bias offset of the data IIRC. Like the O2 sensor and temp sensors.
Are you at a high altitude, or have large tires or re-gearing that creates the higher NOx problem?
Ecomike
NAXJA# 2091
- Location
- MilkyWay Galaxy
No that leak past the cat would not affect anything NOx wise.
I've run it through a couple of years ago, not recently, however. That's on my list of stuff to try, although I have my doubts about it being a solution.
(I say this, because the throttle response suggests to me that it's a little lean, yet the O2 sensor is cycling...just seems to be doing it awfully slowly for an MPI system)
Negative. I'll talk to my muffler shop about it.
The grounds for the ECU are at the right rear of the block (down below the #5 plug); those have been cleaned/snugged. However, I'm going to take a closer look here, in case one of the crimps has started to corrode or something like it.
There is an awful lot of positive-spiking electrical noise on the O2 sensor signal that has me concerned, and which is not present on the MAP sensor, suggesting that it's local to the O2 sensor circuit. Besides the slow O2 sensor cycling, it shows it on the rich (positive) side of the duty cycle more than I would expect for the way that it's behaving (e.g. if it's really running lean, I would expect just the opposite). Yet, you can clearly see a rich-going spike when the throttle is opened, and 100% lean as the throttle is closed (fuel shut off until speed drops back into idle range). I'm just guessing that if the ECU thinks it's richer than it really is, I could get these symptoms.
FWIW, I did just pick up an NGK O2 sensor, to see if it's any happier with it. Hate to throw money at stuff, but everything else measurable seems normal.
Negative there, we're at about 1300' MSL, gearing and wheel size are stock, and tire pressures are standard.
Thanks for the suggestions, most appreciated.
I lied earlier.
Remember, this is a 1994 HO setup, Mopar MPI, not Renix
ECU *signal* ground ties to the right rear of the block, along with power. ECU *sensor* ground doesn't appear to actually take a body ground anywhere according to the schematics. TransControl, CamPS, speed, TPS, ECT, AIT, MAP, CPS, and O2 all come together to pin 4 of the ECU, and that's it. If there's a body ground for it, it sure isn't shown (and it might not take one for ground-loop reasons...)
95XJmatt posted a MAP curve on 1/8/14 that looks different from mine on the surface. FSM tells you next to nothing here, other than 1.5-2V at idle (mine runs 1.5 at idle, 16-17" suction). I'll plug this into a curve, and see how mine compares.
Remember, this is a 1994 HO setup, Mopar MPI, not Renix
ECU *signal* ground ties to the right rear of the block, along with power. ECU *sensor* ground doesn't appear to actually take a body ground anywhere according to the schematics. TransControl, CamPS, speed, TPS, ECT, AIT, MAP, CPS, and O2 all come together to pin 4 of the ECU, and that's it. If there's a body ground for it, it sure isn't shown (and it might not take one for ground-loop reasons...)
95XJmatt posted a MAP curve on 1/8/14 that looks different from mine on the surface. FSM tells you next to nothing here, other than 1.5-2V at idle (mine runs 1.5 at idle, 16-17" suction). I'll plug this into a curve, and see how mine compares.
Chrispy93GC
NAXJA Forum User
- Location
- So Cal
What really helped me pass my 93 Grand with 31x10.50 tires stock 4.0 motor with 245,xxx mi NOX 15mph 1200s 25mph 1500s was:
Walker California approved cat. (changed this first put 100mi on it and the NOX #s were worse)
NO exhaust leaks pre catalytic converter
Temporarily blocking the fuel pressure reg. vacuum line to raise the fuel pressure to 41psi (stock regulator)
180° thermostat
Correct Champion plugs gapped to .035"
New fuel filter
The NOX #s went to 15mph 93 25mph 84, C.O. .04 and .05, HC 30 and 21
This the second smog on this Jeep done in this manner and I couldn't be happier.
Hope this helps
Chrispy
Walker California approved cat. (changed this first put 100mi on it and the NOX #s were worse)
NO exhaust leaks pre catalytic converter
Temporarily blocking the fuel pressure reg. vacuum line to raise the fuel pressure to 41psi (stock regulator)
180° thermostat
Correct Champion plugs gapped to .035"
New fuel filter
The NOX #s went to 15mph 93 25mph 84, C.O. .04 and .05, HC 30 and 21
This the second smog on this Jeep done in this manner and I couldn't be happier.
Hope this helps
Chrispy
Interesting data point...
This afternoon, before doing other things, I went ahead and washed the throttle body out and ran some Seafoam down the intake for awhile, in an attempt to try and clean some carbon out. Took awhile, it sat and idled much of the time, and warmed up quite a bit in the process.
Took it out and drove it a bit to make sure it was cleaned out. Temperature gauge never really came down. After about 10 minutes driving, it threw a code and went open-loop. Pulled over and checked the code, it's a 51 (O2 sensor output stuck on lean side). Restarted (CE light back out), drove 5 more, then the light came back, thus I assume the sensor stayed stuck.
Went back to the garage and hooked up the o-scope to the O2 output, and it's stuck at about 330mV. That would definitely be "stuck lean". Shut it off and it actually went to about -80mV (yes, -80, not a typo!).
After cooling off some, the O2 sensor very slowly came back up to it's normal resting output of +100mV. Turn the key on, and it comes up to the ECU bias of 410 or so. Restarted, and it started cycling slowly again after 30 seconds.
How the sensor could output a slightly negative voltage is really odd. Don't know why, presuming the ECU bias + that output would be about 330mV.
I have a new NTK to go in it this weekend, we'll see what that does.
This afternoon, before doing other things, I went ahead and washed the throttle body out and ran some Seafoam down the intake for awhile, in an attempt to try and clean some carbon out. Took awhile, it sat and idled much of the time, and warmed up quite a bit in the process.
Took it out and drove it a bit to make sure it was cleaned out. Temperature gauge never really came down. After about 10 minutes driving, it threw a code and went open-loop. Pulled over and checked the code, it's a 51 (O2 sensor output stuck on lean side). Restarted (CE light back out), drove 5 more, then the light came back, thus I assume the sensor stayed stuck.
Went back to the garage and hooked up the o-scope to the O2 output, and it's stuck at about 330mV. That would definitely be "stuck lean". Shut it off and it actually went to about -80mV (yes, -80, not a typo!).
After cooling off some, the O2 sensor very slowly came back up to it's normal resting output of +100mV. Turn the key on, and it comes up to the ECU bias of 410 or so. Restarted, and it started cycling slowly again after 30 seconds.
How the sensor could output a slightly negative voltage is really odd. Don't know why, presuming the ECU bias + that output would be about 330mV.
I have a new NTK to go in it this weekend, we'll see what that does.
So, finally have an OK IM147 test report in my hand.
Since the last update, I'd installed a new NTK 23023 O2 sensor plus a new manifold/downpipe donut. The NTK sensor does switch quite a bit faster, but still seemed to show it trying to run a bit on the rich side. Results (remember, this is the AZ IM147 test, not a CA test, results are in grams/mile, and CO2 not given):
HC = 0.55 (1.6 limit)
CO = 6.83 (20.00 limit)
NoX = 3.25 (3.0 limit)
New catalyst went on, drove it 50 miles or so yesterday afternoon, then retested today after about 25 mixed city/highway miles, then never shut it off in the test line to keep it hot. Results:
HC = 0.13
CO = 2.84
NoX = 1.10
Muffler shop did say that it was carboned up pretty well. I'd like to say it breathes better, but honestly, after fooling with it so long, I can't tell. I'm guessing that excess heat and backpressure is what caused the prior O2 sensor to freak out, but, who can be sure?
Hope the data helps someone else out.
Since the last update, I'd installed a new NTK 23023 O2 sensor plus a new manifold/downpipe donut. The NTK sensor does switch quite a bit faster, but still seemed to show it trying to run a bit on the rich side. Results (remember, this is the AZ IM147 test, not a CA test, results are in grams/mile, and CO2 not given):
HC = 0.55 (1.6 limit)
CO = 6.83 (20.00 limit)
NoX = 3.25 (3.0 limit)
New catalyst went on, drove it 50 miles or so yesterday afternoon, then retested today after about 25 mixed city/highway miles, then never shut it off in the test line to keep it hot. Results:
HC = 0.13
CO = 2.84
NoX = 1.10
Muffler shop did say that it was carboned up pretty well. I'd like to say it breathes better, but honestly, after fooling with it so long, I can't tell. I'm guessing that excess heat and backpressure is what caused the prior O2 sensor to freak out, but, who can be sure?
Hope the data helps someone else out.
jeepsrock
NAXJA Forum User
- Location
- LA California
Hello and Happy new years to everyone 
In the last few weeks I have done the following,
1. New distributor cap and rotor
2. New spark plugs (Autolite 985) and Wireset (see old plugs picture)
3. New fuel filter
4. Tested CTS and MAP sensor with meter
5. Further checked vacuum hoses
6. Fresh Oil and air/oil filter change
7. Checked distr position which looks correct for 0deg (see picture)
Took it in and failed again once again to excessive nox.. Surprise surprise !! Same problem since my first post several years ago :/
I dropped the Jeep off at a mechanic and he connected it to a snap on diagnostic system and read all the sensors, said it was switching from rich to lean properly and that all seemed to be in order. In fact he was impressed and couldn't find any reason why it would fail so far...
Any suggestions would be extremely helpful here guys..
Thanks.
Pete
Sent from my Moto G (4) using Tapatalk
In the last few weeks I have done the following,
1. New distributor cap and rotor
2. New spark plugs (Autolite 985) and Wireset (see old plugs picture)
3. New fuel filter
4. Tested CTS and MAP sensor with meter
5. Further checked vacuum hoses
6. Fresh Oil and air/oil filter change
7. Checked distr position which looks correct for 0deg (see picture)
Took it in and failed again once again to excessive nox.. Surprise surprise !! Same problem since my first post several years ago :/
I dropped the Jeep off at a mechanic and he connected it to a snap on diagnostic system and read all the sensors, said it was switching from rich to lean properly and that all seemed to be in order. In fact he was impressed and couldn't find any reason why it would fail so far...
Any suggestions would be extremely helpful here guys..
Thanks.
Pete
Sent from my Moto G (4) using Tapatalk
Ecomike
NAXJA# 2091
- Location
- MilkyWay Galaxy
What year is the jeep?
Could be a worn out Cat converter and or slow O2 sensor, that is not bad enough to throw a code.
Have you tried a one stage colder spark plug?
Also check the MAT/IAT temp sensor. It is often overlooked!!
Could be a worn out Cat converter and or slow O2 sensor, that is not bad enough to throw a code.
Have you tried a one stage colder spark plug?
Also check the MAT/IAT temp sensor. It is often overlooked!!
jeepsrock
NAXJA Forum User
- Location
- LA California
The oxygen sensor is new genuine Mopar one (56028301) and CAT is a few years old Magnaflow 39005 :doh:
Pete
Pete
Ecomike
NAXJA# 2091
- Location
- MilkyWay Galaxy
Then I would try running an injector cleaner, and head cleaner like gum out, to remove any carbon from combustion chambers (it raises NOx!!!) and try a colder spark plug.
Before I tried a new Cat.
If you ran it rich with a bad O2 sensor before replacing the O2 senosr, it could have damaged the "few years old" cat very quickly?
I would sure clean and test that IAT/MAT sensor. It controls part of the computer calculations, along with the MAP sensor that could make it run a wee bit lean. No one ever thinks to check it. Just dawned on me today, it could be the missing link. They get dirty and cause some reading errors as they get fouled. Maybe enough to cause the notorious California NOx test problems?????
jeepsrock
NAXJA Forum User
- Location
- LA California
Thanks for the information Ecomike..
What strikes me as odd is if disconnecting the coolant sensor allows the numbers to go down a lot, correct me if I'm wrong, that means the cat is able to do its job and the engine is just running excessively lean?
I definitely tried water and seafoam down the booster vacuum hose a few times before and if u look back it did little to change the numbers
Below are the results from the last test, as you can see everything is running within range and pretty low except the NOX. This is after the tune up, new mopar o2 and cts/map sensor testing.
I also picked the Jeep from the mechanic today and after spending nearly a week with it he feels it's fuel system related and is suggesting to replace the fuel injectors. What is ur guys opinion on this?
What are some good replacements ones if so?
This mystery just keeps getting better and better
Thanks,
Pete
Sent from my Moto G (4) using Tapatalk
What strikes me as odd is if disconnecting the coolant sensor allows the numbers to go down a lot, correct me if I'm wrong, that means the cat is able to do its job and the engine is just running excessively lean?
I definitely tried water and seafoam down the booster vacuum hose a few times before and if u look back it did little to change the numbers
Below are the results from the last test, as you can see everything is running within range and pretty low except the NOX. This is after the tune up, new mopar o2 and cts/map sensor testing.
I also picked the Jeep from the mechanic today and after spending nearly a week with it he feels it's fuel system related and is suggesting to replace the fuel injectors. What is ur guys opinion on this?
What are some good replacements ones if so?
This mystery just keeps getting better and better
Thanks,
Pete
Sent from my Moto G (4) using Tapatalk
Ecomike
NAXJA# 2091
- Location
- MilkyWay Galaxy
Did you try this yet? I suggest it again based on your CTS disconnection question
"I would sure clean and test that IAT/MAT sensor. It controls part of the computer calculations, along with the MAP sensor that could make it run a wee bit lean. No one ever thinks to check it. Just dawned on me today, it could be the missing link. They get dirty and cause some reading errors as they get fouled. Maybe enough to cause the notorious California NOx test problems????? "
Is the CTS giving the proper resistance at operating temperature?
"I would sure clean and test that IAT/MAT sensor. It controls part of the computer calculations, along with the MAP sensor that could make it run a wee bit lean. No one ever thinks to check it. Just dawned on me today, it could be the missing link. They get dirty and cause some reading errors as they get fouled. Maybe enough to cause the notorious California NOx test problems????? "
Is the CTS giving the proper resistance at operating temperature?
Thanks for the information Ecomike..
What strikes me as odd is if disconnecting the coolant sensor allows the numbers to go down a lot, correct me if I'm wrong, that means the cat is able to do its job and the engine is just running excessively lean?
I definitely tried water and seafoam down the booster vacuum hose a few times before and if u look back it did little to change the numbers
Below are the results from the last test, as you can see everything is running within range and pretty low except the NOX. This is after the tune up, new mopar o2 and cts/map sensor testing.
I also picked the Jeep from the mechanic today and after spending nearly a week with it he feels it's fuel system related and is suggesting to replace the fuel injectors. What is ur guys opinion on this?
What are some good replacements ones if so?
This mystery just keeps getting better and better
Thanks,
Pete
Sent from my Moto G (4) using Tapatalk
snooop1e
NAXJA Forum User
- Location
- California
@jeepsrock
I have a 94 Jeep YJ, with K&N FIPK intake, Fastman 62mmThrottle Body and Borla header, 192k miles. Engine is clean as a whistle, only had synthetic oil (every 6k miles) Until this year my smog tests were perfect (Nox in double digits) and always passed with ease. This year I failed with very high Nox (15mph =1600 and 25Mph =1500) all other numbers were exactly the same as when I passed last year.
Since that first test I have installed new,
Water pump
Thermostat (195)
MagnaFlow 3 way (CARB Approved) CAT
NTK oxygen Sensor
Fuel filter
CTS (thermostat housing)
CTS (Engine block)
AIC
MAP
Champion Copper Spark Plugs .035 gap
Fuel Pressure Regulator
Distributor Cap
Rotor
Wires
I ran a fuel pressure check and idle was 31psi. When I pulled the vacuum hose to the pressure regulator the fuel pressure only increased by 5 or 6 psi (not the recommended 8-10 psi)
I have run Sea foam through the brake booster vacuum hose and 2 bottles of CRC GTP through the fuel (91 Octane Chevron Techron)
After spending approx $1000.00 and failing my 5th smog test today for High Nox (15mph =1500, 25mph=1240) I waved the white flag and dropped it off at a smog test and repair shop. If it passes I am going to sell it.
Anyone outside CA want a very well maintained YJ? (engine is immaculate) Brown dog motor mounts, new Rancho shocks, old man Emu leafs, American Racing cast wheels (31 inch) w/BF Goodrich All Terrains (practically new) Leather wrapped Grant steering wheel. Borla Header, Fastman 62mm throttle body, K&N FIPK, OPTIMA Red Battery, New Flowmaster Super 44, New water pump, new clutch slave cylinder, new MagnaFlow 3 way CAT, Never been off roading, does not burn oil (never has) no leaks and no squeaks... I have babied her, 2nd owner. I have new Drums ( with all new internals) still in the boxes and new rotors that are still in the original packaging waiting to be installed. . Make me an offer. In California she is a lump of coal, outside California she is gem.
I'm tired of this crap, nobody should have to work this hard, spend this much money and experience so much stress just to keep a perfectly running car "legal". Cant wait to move out of the PRK (Peoples Republic of Kalifornia) I love my Jeep but I have bills to pay and I need to be able to drive to work. If she doesn't pass I will have to let her go. What a waste..
Sorry for the rant but i am mentally drained over this. Will let you guys know if the "repair station" can get her to pass. If not I will have to turn her over to the State for destruction...Breaks my heart. Stick a fork in me, I'm done :hang:
I have a 94 Jeep YJ, with K&N FIPK intake, Fastman 62mmThrottle Body and Borla header, 192k miles. Engine is clean as a whistle, only had synthetic oil (every 6k miles) Until this year my smog tests were perfect (Nox in double digits) and always passed with ease. This year I failed with very high Nox (15mph =1600 and 25Mph =1500) all other numbers were exactly the same as when I passed last year.
Since that first test I have installed new,
Water pump
Thermostat (195)
MagnaFlow 3 way (CARB Approved) CAT
NTK oxygen Sensor
Fuel filter
CTS (thermostat housing)
CTS (Engine block)
AIC
MAP
Champion Copper Spark Plugs .035 gap
Fuel Pressure Regulator
Distributor Cap
Rotor
Wires
I ran a fuel pressure check and idle was 31psi. When I pulled the vacuum hose to the pressure regulator the fuel pressure only increased by 5 or 6 psi (not the recommended 8-10 psi)
I have run Sea foam through the brake booster vacuum hose and 2 bottles of CRC GTP through the fuel (91 Octane Chevron Techron)
After spending approx $1000.00 and failing my 5th smog test today for High Nox (15mph =1500, 25mph=1240) I waved the white flag and dropped it off at a smog test and repair shop. If it passes I am going to sell it.
Anyone outside CA want a very well maintained YJ? (engine is immaculate) Brown dog motor mounts, new Rancho shocks, old man Emu leafs, American Racing cast wheels (31 inch) w/BF Goodrich All Terrains (practically new) Leather wrapped Grant steering wheel. Borla Header, Fastman 62mm throttle body, K&N FIPK, OPTIMA Red Battery, New Flowmaster Super 44, New water pump, new clutch slave cylinder, new MagnaFlow 3 way CAT, Never been off roading, does not burn oil (never has) no leaks and no squeaks... I have babied her, 2nd owner. I have new Drums ( with all new internals) still in the boxes and new rotors that are still in the original packaging waiting to be installed. . Make me an offer. In California she is a lump of coal, outside California she is gem.
I'm tired of this crap, nobody should have to work this hard, spend this much money and experience so much stress just to keep a perfectly running car "legal". Cant wait to move out of the PRK (Peoples Republic of Kalifornia) I love my Jeep but I have bills to pay and I need to be able to drive to work. If she doesn't pass I will have to let her go. What a waste..
Sorry for the rant but i am mentally drained over this. Will let you guys know if the "repair station" can get her to pass. If not I will have to turn her over to the State for destruction...Breaks my heart. Stick a fork in me, I'm done :hang:
Last edited:
Ecomike
NAXJA# 2091
- Location
- MilkyWay Galaxy
Sounds like the fuel pressure is too low, and making the engine run lean to me. Wish you had posted here before you spent all that money. Could be a leaking fuel hose in the gas tank on the fuel pump outlet side. The newer gasoline and age (1994, 22 years old) do a number on the old fuel hoses in the gas tanks. And the fuel pump may be wearing out.
Did you make any changes or repairs since the last good smog test?
You should have no problem selling that rig to others as is.
Did you make any changes or repairs since the last good smog test?
You should have no problem selling that rig to others as is.
snooop1e
NAXJA Forum User
- Location
- California
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!
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!
