California smog expert please advise

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brave sir robin

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So my Pathfinder failed its biannual smog test the other day. The truck runs great and does not run hot or have any performance issues whatsoever (aside from only having 150hp to push around two tons). Before the test the engine was at full operating temp and had been driven pretty hard by me on the trip to the shop.


It failed because NOX was too high at 15mph

MAX 350 ppm measured 609 ppm

passed at 25mph
MAX 527 ppm measured 252 ppm

I included a picture because I know some people are going to ask about other readings.

Going to remove and clean the EGR valve this weekend because I have never had it out.


VYZYhju.jpg







any help would be greatly appreciated
 
Your HC and CO are both low when NOX high, that usually means you are running lean, too hot, or has an intake leak. That happened to me once and I think on the retest I did an oil change, 91 gas, 1 bottle of Techron / Regane in the last tank of gas, and new plugs and it pass with no problem.
 
Last edited:
Turn the idle mixture out a turn
grin2.gif
Just foolin'. High NOx, low HC and CO. Running hot and lean. Would start by testing the O2 sensor
 
Originally Posted By: brave sir robin
So my Pathfinder failed its biannual smog test the other day.


Bi-annual smog test? Ugh..

I thought it bad enough when N.J. did that annually, BC. (Before Christie).
grin.gif
 
Btw, the advantage of the fuel injector service at Walmart is that they perform a combustion chamber cleaning with a metered cleaner.

Compared to running a tank of Gumout or CRC, the cleaning will be complete sooner and in my one experience was more effective. There is no harm in doing both though.
 
Originally Posted By: Rock_Hudstone
Originally Posted By: brave sir robin
So my Pathfinder failed its biannual smog test the other day.


Bi-annual smog test? Ugh..

I thought it bad enough when N.J. did that annually, BC. (Before Christie).
grin.gif



It's every two years, not twice a year!
 
EGR system may be clogged. If you force open the EGR valve at idle, the engine should stumble badly and/or stall.
 
Originally Posted By: CharlieBauer
Can you also post up your previous smog test results?

I accidentally tossed the previous test but I do remember it barely passing the same NOX test (15mph) prolly around 300ppm

Up until recently the truck only got driven every few weeks for brief offroading. It amounted to around 500 miles a year LOL

a few months ago I replaced the timing belt cuz....old (the belt was immaculate btw) replaced water pump and fan clutch. Spark plugs and rotor a year and maybe 1k miles ago (just cuz).

Like I said before the truck runs great though after adding an extra ground wire to the MAF sensor the idle jumped almost 100rpm. its now around 850rpm when fully warmed up.


I normally would be hunting for vacuum leaks and I in fact did one on the EGR itself (before the test) but it runs so smoothly for having 203k miles and beaten on by me I just don't know...


so far no calls for a new cat so I guess thats good LOL

9xPPfNv.jpg
 
Quote:
Like I said before the truck runs great though after adding an extra ground wire to the MAF sensor the idle jumped almost 100rpm. its now around 850rpm when fully warmed up.


That's your clue right there. That extra oxygen gotta do something to the NOX reading after burning slightly lean. If I were you I'd figure out why it is 100rpm higher now, and what I can do / fix to make it back to 750rpm.

Maybe you can adjust the idle or find and fix the intake leak? or retard the ignition a bit?
 
Originally Posted By: brave sir robin
Originally Posted By: CharlieBauer
Can you also post up your previous smog test results?

I accidentally tossed the previous test but I do remember it barely passing the same NOX test (15mph) prolly around 300ppm

Up until recently the truck only got driven every few weeks for brief offroading. It amounted to around 500 miles a year LOL

a few months ago I replaced the timing belt cuz....old (the belt was immaculate btw) replaced water pump and fan clutch. Spark plugs and rotor a year and maybe 1k miles ago (just cuz).

Like I said before the truck runs great though after adding an extra ground wire to the MAF sensor the idle jumped almost 100rpm. its now around 850rpm when fully warmed up.


I normally would be hunting for vacuum leaks and I in fact did one on the EGR itself (before the test) but it runs so smoothly for having 203k miles and beaten on by me I just don't know...


so far no calls for a new cat so I guess thats good LOL

9xPPfNv.jpg



Nice car! I love me a nice hardbody, you never see them here anymore.
 
Cool 'er off! Maybe run pure water in the radiator for the test. Even if your overall temp looks the same it could be a hair cooler by the water jackets.
 
Originally Posted By: eljefino
Cool 'er off! Maybe run pure water in the radiator for the test. Even if your overall temp looks the same it could be a hair cooler by the water jackets.


The water pump and fan clutch are around 400 miles old. I also run a 2:1 water to coolant ratio as it is.
 
Originally Posted By: maxdustington
Originally Posted By: brave sir robin
Originally Posted By: CharlieBauer
Can you also post up your previous smog test results?

I accidentally tossed the previous test but I do remember it barely passing the same NOX test (15mph) prolly around 300ppm

Up until recently the truck only got driven every few weeks for brief offroading. It amounted to around 500 miles a year LOL

a few months ago I replaced the timing belt cuz....old (the belt was immaculate btw) replaced water pump and fan clutch. Spark plugs and rotor a year and maybe 1k miles ago (just cuz).

Like I said before the truck runs great though after adding an extra ground wire to the MAF sensor the idle jumped almost 100rpm. its now around 850rpm when fully warmed up.


I normally would be hunting for vacuum leaks and I in fact did one on the EGR itself (before the test) but it runs so smoothly for having 203k miles and beaten on by me I just don't know...


so far no calls for a new cat so I guess thats good LOL

9xPPfNv.jpg



Nice car! I love me a nice hardbody, you never see them here anymore.


I'm a big fan of them too and in some ways they are still fairly advanced. The adjustable suspension on mine still works (barely). They have never been very stylish but they are still legit real actual trucks underneath. Trucks that still handle surprisingly well on the road btw. My brother drives a mid 2000s Range Rover and he says it handles nearly the same with the main difference being tires.
He's the most reliable vehicle I have ever owned so when I failed smog it surprised me LOL
 
Originally Posted By: PandaBear
Quote:
Like I said before the truck runs great though after adding an extra ground wire to the MAF sensor the idle jumped almost 100rpm. its now around 850rpm when fully warmed up.


That's your clue right there. That extra oxygen gotta do something to the NOX reading after burning slightly lean. If I were you I'd figure out why it is 100rpm higher now, and what I can do / fix to make it back to 750rpm.

Maybe you can adjust the idle or find and fix the intake leak? or retard the ignition a bit?


I don't think having a cleaner ground is going to throw off emissions. If anything it should improve things by having a more consistent signal.

I'm going to triple check all the vacuum lines tomorrow morning but it does not act like it has a vacuum leak. The idle is rock steady aside from occasional changes induced from the idle control system. It doesn't flutter at all and for an old V6 its smooth as warm butter the gearshift barely wiggles at idle.



I'm hanging my hopes on the EGR system being clogged up from being 22 years old and never being touched with almost 90% city and off road driving.
 
Originally Posted By: Rock_Hudstone
failed its biannual smog test

Bi-annual smog test? Ugh.. [/quote]

UGGGH is right!! I shall never live in California.
 
Originally Posted By: Linctex
Originally Posted By: Rock_Hudstone
failed its biannual smog test

Bi-annual smog test? Ugh..


UGGGH is right!! I shall never live in California.

[/quote]

tbh the auto laws could be a lot worse.
It's the firearms laws that are going to convince me to leave.
 
This is a trick I did to 3 ’98 Chev Lumina sedans and other cars that had super high NOX but good on all other numbers:

You could have a dead cat converter that can cause the hi NOX.

Lean / too lean mixtures often get an undetectable ‘lean miss’ where HC, NOX can both be high at the same time.

In the '98 Lumina V6, the EGR (with stepper motor) sits on a gasket right on top of the ports to the exhaust and intake, the valve is in the EGR body, I took a sharp box cutter type blade and cut a groove from Exhaust to Intake about .020” wide x .020” deep. Then I popped the EGR back on tightened it down. Never cut a groove to outside edge of the gasket, that would amount to a vacuum leak to the atmosphere that would make things worse.

What I did was provide “uncommanded EGR gas” at all engine speeds including idle, but not enough to make the engine stumble. Thus the NOX dropped from 900 ppms to 330 ppms! Nothing else was changed. Your HC may climb 1-4 ppms, but you have room on your report.

If you have vacuum operated EGR or an EGR with a long spindle that extends into the manifold, then I would remove it and measure the fully extended length and add extra gaskets so the valve tip sits off it’s seat with a .002” to .005” gap.

On a 1987 Chrysler 318 V8 I located the EGR vacuum bleed solenoid controlled by the computer, it had a small foam filter on top, I pulled that off and put adhesive tape over the port blocking it, then poked a hole with a needle .020” dia, this means the EGR line holds about 2 to 5” of vacuum keeping the EGR cracked open by a hair! That killed off 50% of the NOX numbers at the time on a bad cat and made legal clean exhaust! That design took a while to come up with and 10 minutes to do! I put the foam back on the Tech never knew!

Remember, in general EGRs aren’t supposed to open until 2,500 RPMs or more! This way you keep all NOX way lower! Up here in Canada NOX is measured at idle too, which can be tough for old carbs, since idle circuits aren’t too precise!

I did this up to 6 yrs ago, never took Pics back then! My current ride has no EGR!
 
Originally Posted By: brave sir robin
I'm hanging my hopes on the EGR system being clogged up from being 22 years old and never being touched with almost 90% city and off road driving.



City driving / short trips and non top tier fuel will also cause carbon to build up in the combustion chamber.

You may as well throw Gumout All In One (the one that treats 35 gallons) or CRC guaranteed to pass (can get your money back if it doesn't), or even the Walmart $20 fuel injector service that cleans up the combustion chamber.

None of these would be wasted maintenance items outside of doing them for a smog test.
 
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