New-to-me LX470 failing CO emissions due to NOx (1 Viewer)

[marcovasqz]

Hello all!
My wife and I have a 11 years olds and I finally convinced her to get my dream truck: a Land Cruiser. We scored a rust free LX470 with 221k miles:

The main purpose of this truck will be family hauler (I have a Xterra for off-roading), so I have to keep this truck as comfortable and reliable as possible.

I’m planning on doing everything myself if possible. On my list I have regular maintenance first, starting with all fluids replaced. Then I want to work in AHC, since it feels bouncy at the moment.

But before anything I want to register this truck, and I can’t do it due to failing emissions:

Google search indicates it’s related to EGR system. I found the schematic of this system:

Has anyone dealt with failed emissions due NOx? I found several threads in 80 series… but only one in 100 series.

Where should I start? I was thinking in replacing VSV, but dad thinks I should start with PCV.

Thank you!

 

[kerrye]

You are not failing by much. Looking at your graph I suspect the NOX peaks are occurring immediately upon upshifts. I would turn off the overdrive and turn on the power button and run it through the test again. You will have one less shift and all your shifts will occur at higher rpm's/speed. I strongly suspect this will reduce NOX emissions, at least to some degree. I don't know if it will reduce them enough to pass, but you don't need to reduce them much. In any case, your second test is free and even if you fail you will at least have two graphs of two different driving patterns to compare NOX readings.

 

[marcovasqz]

You are not failing by much. Looking at your graph I suspect the NOX peaks are occurring immediately upon upshifts. I would turn off the overdrive and turn on the power button and run it through the test again. You will have one less shift and all your shifts will occur at higher rpm's/speed. I strongly suspect this will reduce NOX emissions, at least to some degree. I don't know if it will reduce them enough to pass, but you don't need to reduce them much. In any case, your second test is free and even if you fail you will at least have two graphs of two different driving patterns to compare NOX readings.

I know… it barely failed. That’s a great observation!

I did try that just now, and I noticed the OD is reset when engine is off, which they made me do during the test. But power button remained on… is it still worth giving it a try without OD?

I indeed would love to get to pass the test, but I wouldn’t mind finding the root cause of the problem just so I don’t need to worry about it for next test.

 

[kerrye]

I wasn't aware that the OD turned back on when the engine was restarted. It stayed off on my 80 series. I think it is worth a shot with the power button on. High NOX readings are caused by high temperatures and pressures in the cylinders. On other vehicles the EGR system is designed to reduce these but the 100 series has no EGR system. I believe a lean mixture can cause higher NOX but also the CAT's on a 100 series are designed to reduce NOX I think (unlike the oe cats on 80 series). I believe I read somewhere a suggestion that low fuel pressure may result in a lean mixture which might increase NOX. For comparison purposes, my 2002 LX470 recently tested at .64 NOX. By the way, in my experience, Colorado's emissions testing does not produce repeatable results. I ran my 80 series through the test twice within 20 minutes (the gas cap failed back when they tested the cap after the dyne test) and the results were vastly different. I suspect that the difference is at least partly dependent on how the vehicle is driven on the dyne.

 

[kevgentile]

It'd be helpful if the emissions station provided the A/F ratio. We rarely use our machines these days since Maryland no longer runs the dyno's. All pre-obd2's are static tests and obd2's are just plug-in to check faults and readiness.
Some live data from techstream or any capable diag can help trouble shoot maf and cat/primary o2 health. Run a smoke test to rule out any small vac leaks and might find a shop to read out your a/f ratio.

 

[kerrye]

If you end up taking it to a shop, Urban Auto Care on East Evans (formerly Comprehensive Car Care) has done quality work on our 80 Series.

 

[marcovasqz]

If you end up taking it to a shop, Urban Auto Care on East Evans (formerly Comprehensive Car Care) has done quality work on our 80 Series.

I’ll keep this in mind.

I’m waiting for a few parts I ordered to do a tune up myself and I’m going to give it another try…

I’ll update results

 

[vipergrhd]

When you are ready to do another smog drive it like you stole it and get the CAT hot.

 

[imhighlander]

I'll bet dollars to donuts it's the MAF. I chased down high NOx for Colorado front range emissions from December until now and just passed a couple of weeks ago. (FINALLY!!) Mine is a JDM imported 1998 LC with 70,000 miles and because it's gray market, there's no OBDII connector to run any diagnostics. I was basically diagnosing by symptom.

I ended up replacing spark plugs, cleaning the throttle body, cleaning the MAF, and ultimately replacing the catalytic converters. The catalysts were definitely shot (sounded like they were full of gravel), but even after all that I failed emissions two more times. I swapped out the MAF thinking that it wasn't providing accurate information to the ECU and thus not providing accurate fuel/air mix. That solved it.

Grab a new MAF and plug it in, and then retest. I'll buy you a beer if that doesn't solve it. (But you have to come up to Evergreen for it.)

 

[marcovasqz]

I decided to replace the PCV valve, thinking it was going to be simple and cheap enough to do before test (big mistake)... So I tried to be careful with the grommet but it fell apart.... I picked what I could, then vacuumed it, but I'm now paranoid there's pieces that fell in there:

For my mind sake, I'll just go ahead and remove valve cover for my mind sake. Buying gaskets, spark plug seals, FIPG and everything else I will replace while doing this.

I know... This was unnecessary...

I'll bet dollars to donuts it's the MAF. I chased down high NOx for Colorado front range emissions from December until now and just passed a couple of weeks ago. (FINALLY!!) Mine is a JDM imported 1998 LC with 70,000 miles and because it's gray market, there's no OBDII connector to run any diagnostics. I was basically diagnosing by symptom.

I ended up replacing spark plugs, cleaning the throttle body, cleaning the MAF, and ultimately replacing the catalytic converters. The catalysts were definitely shot (sounded like they were full of gravel), but even after all that I failed emissions two more times. I swapped out the MAF thinking that it wasn't providing accurate information to the ECU and thus not providing accurate fuel/air mix. That solved it.

Grab a new MAF and plug it in, and then retest. I'll buy you a beer if that doesn't solve it. (But you have to come up to Evergreen for it.)

You mean the sensor, right? I didn't fail by much so I think cleaning it will be enough. Wanted to retest this weekend but I don't think that will happen. Sigh....

 

[marcovasqz]

And update....

Here's what I've done to solve my NOx/Emission issue:

Part​	Brand - Part #​
New spark plugs​	Denso - 4702 IK20TT​
New Head Cover Gaskets​	Toyota - 1121350031 / 1121450011​
Several EVAP / Vacuum hoses (Replaced every cracked hose)​	Toyota - 1703050070, 1226250080, 1226150050, 1734150110​
New air filter​	Denso - 1433045​
New O2 Sensors​	Denso - 2344169 / 2344154​
Cleaned Throttle Body and MAF sensor​
Used Cataclean​

I was pretty sure it was going to pass, but I failed again due to NOx, and it was a little worse this time (1.9 GPM).

I'm doing what @imhighlander suggested next and ordered new toyota MAF sensor (2204-75020).

Will update the results... Fingers crossed

 

[marcovasqz]

And update...
Today my lx finally passed emissions.

I finally got the new sensor last night, and I replaced it.

Today I got 0.56 NOx GPM vs 1.9 a week ago. State minimum is 1.5.

Shout out to @imhighlander, I should have started with what you told me to do.

Well at least this confirms it for future 100 owners in CO.

 

[augustwest]

I just failed for NOX for a second time (1.9127). After the first time I replaced the MAF and O2 sensors. Going to replace vacuum piping next.

 

[marcovasqz]

Did you use

I just failed for NOX for a second time (1.9127). After the first time I replaced the MAF and O2 sensors. Going to replace vacuum piping next.

I'm sorry about failing the test...

How much GPM you got at your first test?

Did you use new toyota MAF sensor?

I'm surprised that didn't work for you, it did it for me and others

 

[NoTempoLimit]

High NOx is the result of high combustion temperature, usually due to lean mixture. FWIW: First time I had to do CA emissions (I had a BMW E39) I made the mistake of clearing codes just prior to test and failed for that reason. I put in a bottle of Techron and drove the car over the next two days to re-set the monitors (PITA procedure, mostly LOW speed highway). On re-test the emissions numbers were noticeably lower. No mods at all to the car. This was back before the OBD-II only testing in CA.

 

[augustwest]

High NOx is the result of high combustion temperature, usually due to lean mixture. FWIW: First time I had to do CA emissions (I had a BMW E39) I made the mistake of clearing codes just prior to test and failed for that reason. I put in a bottle of Techron and drove the car over the next two days to re-set the monitors (PITA procedure, mostly LOW speed highway). On re-test the emissions numbers were noticeably lower. No mods at all to the car. This was back before the OBD-II only testing in CA.

Interesting regarding the resetting of the codes. I did reset mine the night before after replacing the O2 sensors. The CEL with P0420 and P0430 codes have not come back since. Usually get the CEL with those codes 1-2 times a day.

 

[augustwest]

Replaced front O2 sensors and various vacuum/air piping/hoses and then still failed for high NOX (1.78). I don't know what else to try than replacing the cats. So far, in addition to these last couple things, I've also replaced the rear O2 senors, MAF sensor. Still no CEL or codes since replacing the front 02 and MAF sensors.

 

[marcovasqz]

The CEL with P0420 and P0430 codes have not come back since. Usually get the CEL with those codes 1-2 times a day.

These exact codes showed up in my Xterra a few hours after buying it. Somehow I passed emission with the CEL on. (The exact same test center where I failed twice with the LX). But later I replaced them and codes never came back.

I never had CEL codes in LX, but those are two pricey ones to fix. I'm sorry about it...

 

[augustwest]

These exact codes showed up in my Xterra a few hours after buying it. Somehow I passed emission with the CEL on. (The exact same test center where I failed twice with the LX). But later I replaced them and codes never came back.

I never had CEL codes in LX, but those are two pricey ones to fix. I'm sorry about it...

Yeah, it's a bummer. Working through my options on the cats, which appear to be limited with CO's ridiculous emissions standards.

 

[krispykritter]

I keep seeing this thread pop up so figured I'd throw another data point into here since I've just done my emissions test. As far as I know, all the emissions stuff on the my LX are 100% stock/original and I'm at 196k miles. I just post this as most of my numbers are significantly lower even after you've passed - maybe there's an issue somewhere? Or maybe just older/less efficient system? No idea, but figured I'd share anyway.