CA SMOG, HIGH NOx

[Ecomike]

Have you run an IR thermal scan on the entire engine, manifolds, etc to look for peak temps and hot spots? You could have a heat soak issue on one or more fuel injectors, turning liquid gasoline to vapor and causing a lean condition.

How hot is the coolant actually getting????? Is the flow blocked in a spot and causing a hotter or leaner cylinder?

 

[jeepsrock]

I am not even sure how to run a IR scan, let alone have the equipment for it, hahaha..I was under the impression that the heat soak issue only mainly existed toward the later years? The jeep runs at normal temperatures, nothing unusual there.

Earlier today I visited my local jeep dealer and they essentially told me they don't work on jeeps that old anymore because they don't have the equipment for them anymore. I called an additional two and they said the same thing. I would love an answer to this crazy puzzle...kinda rediculous at this point.

Does anyone have a dealer or shop recommendation in the Los Angeles area that would be willing to take a whack that I could pay for there time?


Sent from my Pixel XL using Tapatalk

 

[Ecomike]

LOL, if you can afford one of these you are deep shit

http://i85.photobucket.com/albums/k48/blackbeast1/blower motor/IMG_2028.jpg

$19.99

Point aim and push the button is a complex process, LOL.

JK

Look for a hot spot cylinder by cylinder, injector by injector.

Have you disconnected one spark plug wire or fuel injector connector at a time to see if doing that makes the engine run worse, confirming that each cylinder is working/firing?

You may have a partly clogged, dirty injector that is putting out too little fuel and making the one cylinder run lean.

The computer and O2 sensor do not work and adjust fuel feed one cylinder at a time, they do an average.

You might try a different brand and part number spark plug even.

 

[Ecomike]

The Older rigs run at a lower fuel pressure, so a heat soak issue can happen easier with them, if they get too hot. But once started, I doubt that is the high NOx issue.

You got a tough one for sure. Last guy replaced his seemingly working NTK O2 sensor with Bosch (which is heresy according to Cruiser54 brand wise and his NOx dropped 95% LOL).

At this point I would probably start replacing parts, the cheapest ones first like the CTS and IAT.

Make a window distr cap and check the mechanical spark timing.

Try running it with a new CTS, what have you got loose? Test the CTS wiring it self. Wiggle the wiring harness with a helper and see if the CTS ground wire value changes, or back probe the sensor on volts and see what the voltage reading is while the jeep warms up, and while wiggling the wires. See if there is an actual full 5 volts getting to the CTS hot wire at the sensor. And see if the ground wire is actually showing less than one home all the way to the negative post at the battery

I am not even sure how to run a IR scan, let alone have the equipment for it, hahaha..I was under the impression that the heat soak issue only mainly existed toward the later years? The jeep runs at normal temperatures, nothing unusual there.

Earlier today I visited my local jeep dealer and they essentially told me they don't work on jeeps that old anymore because they don't have the equipment for them anymore. I called an additional two and they said the same thing. I would love an answer to this crazy puzzle...kinda rediculous at this point.

Does anyone have a dealer or shop recommendation in the Los Angeles area that would be willing to take a whack that I could pay for there time?


Sent from my Pixel XL using Tapatalk

 

[tetatdo]

Welp. I posted in 2014 on this thread about my never ending NOx issues and thought I had it fixed. At the time a new cat, NTK sensor and a new FPR did it.

I failed/passed in 2016 with minimal issues (I had to super heat the cat), passed with no issues in 2018 and in 2020. I thought I had the issue fixed.

Went in for testing last week and failed AGAIN! ARRRRGGGGHH#@$&(%&$@&#$&#@$&@$&


The tech tested twice. First time it looked like it was going to fail on the 15 mph and he aborted. We heated it up (not super heated) and ran it again. it passed 15 mph but failed on the 25 mph

Here's my numbers

CO2% %O2 HC CO NOx
14.9 0 12 .01 270 PASS
14.8 0 11 .01 687 FAIL

Previous years I passed with very low NOX. 2018 I think it was 6ppm on 15mph and 141 ppm on 25mph

Since then, ive only put 3-4k on the jeep. The exhaust system was replaced from header to tail pipe in 2014 and welded by a very very good welder, so i dont think it's leaking

Ive also had to change the CPS, the ignition coil and the fuel pump since then.

I have a DRB II and with that tool you can pull timing. It seemed to help in the past but not this time...

 

[Saudade]

Did I read your thread history correct? You have a ZJ not an XJ?

You don't seem to accumulate a lot of mileage. Do you drive mostly short trips? If so, this can kill a cat quickly since your converter never gets up to full temp and stay there long enough to cook the crud out. This reduces it's efficiency and can contribute to increased NOX.

Run some more seafoam through it including pouring some down the TB. After letting it do it's magic, go for a really long ride at highway speeds to burn it all out.

I go through this every 2 years on my '88 XJ. It fails the first try. I use the results to determine what to do. Then I fix it, retest and pass. I am on my 3rd CAT since 2008 (when they were cheap). I too drive it less than 1000/yr and mostly short trips. Sometimes I don't even get up to full temp. You know how expensive CARB approved CATs are, so do what you can to save it.

There also may some differences in emissions control for a ZJ over an XJ. You should post in a suitable ZJ forum.

 

[tetatdo]

Did I read your thread history correct? You have a ZJ not an XJ?

You don't seem to accumulate a lot of mileage. Do you drive mostly short trips? If so, this can kill a cat quickly since your converter never gets up to full temp and stay there long enough to cook the crud out. This reduces it's efficiency and can contribute to increased NOX.

Run some more seafoam through it including pouring some down the TB. After letting it do it's magic, go for a really long ride at highway speeds to burn it all out.

I go through this every 2 years on my '88 XJ. It fails the first try. I use the results to determine what to do. Then I fix it, retest and pass. I am on my 3rd CAT since 2008 (when they were cheap). I too drive it less than 1000/yr and mostly short trips. Sometimes I don't even get up to full temp. You know how expensive CARB approved CATs are, so do what you can to save it.

There also may some differences in emissions control for a ZJ over an XJ. You should post in a suitable ZJ forum.

Yup ZJ owner here. I believe from 93-95 the ZJ and XJs are very similar if not identical in terms of engine management and emissions. It seems all jeep 4.0s eventually run into a high NOx situation.

As far as short trips. I cant say I take many short trips as I have the opposite use case for my jeep. Roadtrips and the occasional errand. Im pretty sure I get the cat up to temp each use as I live on a hill and any time I return home, its a long way up a hill to get to my house.

 

[tetatdo]

Yup ZJ owner here. I believe from 93-95 the ZJ and XJs are very similar if not identical in terms of engine management and emissions. It seems all jeep 4.0s eventually run into a high NOx situation.

As far as short trips. I cant say I take many short trips as I have the opposite use case for my jeep. Roadtrips and the occasional errand. Im pretty sure I get the cat up to temp each use as I live on a hill and any time I return home, its a long way up a hill to get to my house.

So I stuck a fuel pressure gauge and went for a drive and looks like my fuel pressure is slightly off spec. Im idling at 30 psi (should be 31) and at WOT it gets to about a max of 37-38 psi. 39 PSI is max and if i unplug the vaccum hose to the FPR, it does hit 39 psi.

Under load, say... going up hill around 15 and 25 mph, part throttle, its around 34-35 psi.

Wondering if this might be the cause of my issues

 

[tetatdo]

Well, i looked over a few things on my jeep, including bore scoping the cyls to look for carbon buildup (they were surprisingly clean at 217k miles), changed the fuel filter, tightened up the intake/exhaust manifold bolts and went in for a second test and passed!

I did rev it at about 2k rpm before the rest for 3-5 mins to get the cat super heated.

I still think the problem exists, cuz it blew super clean at 15mph on NOx and then shot up at 25 mph

I also have the 703 injectors, 2.5" exhaust, a 62mm tb, the FIPK and a WJ manifold but those havent stopped me from passing first try in 2018 and 2020.

Here's my numbers:


CO2 O2 HC CO NO
15.1 0 9 .01 50
15.2 0 8 .00 435

If jeepsrock ever comes back around to deal with this in this thread, hit me up. I'm local to you. I actually found this utility on the russian jeep forums that does data logging on obd-1 jeeps! I didnt need to use it to fix my issue but we can get together and check your jeep. I'm local to you in SF valley

 

[Rob Mayercik]

OBD-1 Logging? Very interesting, would like to know more. Got a link?

 

[tetatdo]

OBD-1 Logging? Very interesting, would like to know more. Got a link?

nothing that's useful. Its a russian forum.

I did grab their utility and ran it and got it connected and datalogging. I got a nice graph for the o2 sensor switching. The problem is the entire program is in russian. You have to build a cable to do this, its not very expensive but it requires some work to make it happen.

I had a cable built to talk to the ECU with my laptop for a whole other project I was working on.

Im not a software engineer but I did find a way to disassemble their program and found all the strings. I'm trying to find a way to translate their program and recompile it.

https://www.drive2.com/l/503862474496279278/

 

[DKibbe6800]

Man... I traveled back in time almost 10 years and read all 15 pages of this thread and thought for sure there'd be a solution... :wow:

Don't get me wrong, there is so much good info here. I haven't looked too much into my XJ yet because I wanted to read as much as I could.

I'll report back if/when I pass.

 

[tetatdo]

Man... I traveled back in time almost 10 years and read all 15 pages of this thread and thought for sure there'd be a solution... :wow:

Don't get me wrong, there is so much good info here. I haven't looked too much into my XJ yet because I wanted to read as much as I could.

I'll report back if/when I pass.

godspeed my friend!

I'm no tuner but in my case it seems like if i could just fatten up the fuel curve when its under load, and get the mixture a little richer, i'd have no issues passing.

 

[Saudade]

When you have something to report, PLEASE start a new thread rather than continue to bump this relic. In case you fail, make sure you post all of your smog results, the year of your XJ and other relevant factors.

 

[tetatdo]

any updates @dkibbe6800?