mbomberz1

So, the third time isnt always the charm apparently. Just got done with my 3rd smog attempt and i failed again, barely on NOx. Now I am no smog expert, so I will just tell the story and hopefully you guys see something I don't.

Background on truck:

88 Toyota Pickup, 3vze, 205k miles. Rebuilt motor around 160k. Runs great..

No Engine Codes

Mods:
32x11.5 15 Goodyear kevlar MTR tires
Thorley Headers and 2 1/4 inch exhaust.

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FIRST TEST
Notes:
91 octane
Timing at 12 degrees advanced. (derp)



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SECOND TEST
Notes:
91 Octane
Timing at 9 Degrees advanced. Yay



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THIRD TEST
Notes:
91 Octane
Timing at 9 Degrees advanced.

• New Throttle Body Intake Hose (old one had a crack)
• New EGR Modulator Valve (old one didnt open consistently)
• New Toyota Air filter..
• Completely removed throttle body, cleaned and checked the vacuum lines running to the Modulator valve.
• Readjusted TPS and the idle as I found it to be out of adjustment.
• Tested EGR, its opening and getting vacuum.

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Now it did improve. But the 3rd test was at a different shop. Their scale weighed my truck in at like 650 pounds less, so i think that is why the MAX NOx went down.. My guess is the first shops scale is off. Besides that. I would like to get my nox into good levels instead of trying to just barely pass it. If something is wrong I would like to fix it. Here are some Lambda calculations from the last test. One for the 15 and 25mph test.

15MPH Lambda Calculation:





25MPH Lambda Calculation:





Anything seem suspect here? Anything standing out that I should check? Thanks guys..

RJR

Looks like your O2 sensor control loop is working just fine. The lambda numbers look good. If the EGR is working (and you said you replaced it), I think the next thing I'd check is the cat converter itself.

mbomberz1

Well i only replaced the EGR Modulator Valve, quite a few other EGR parts that i could look into. Next steps i think are to just remove all of the EGR equipment, possibly the intake plenum and really clean them all out. See how much if any gunk is built up there.

The Cat is possible too i guess, its fairly new since my old one was stolen. About 3-4 years ago. probably only 10k miles on this cat though.

scope103

NOx is controlled by the EGR. That's its job. That's its only job.

Your other numbers are all pretty good, so I would concentrate on the EGR. (The cat has a small effect on NOx, but if the cat was bad I would expect more HC.) Run the tests described in the manual. http://personal.utulsa.edu/~nathan-b...77exhaustg.pdf

When I rebuilt my head, I found so much "gunk" in the plenum that it almost completely blocked the tube that admits exhaust into the plenum via the EGR. You can pull the tube going into the plenum; it's about 2mm smaller than the hole and should slide out. Mine was so coated I had to pull it several times to break off enough gunk to get it to come out.

If the EGR exhaust-to-plenum passage is blocked, it won't matter what the EGR valve (and modulator) are doing. Your truck is 6 years older than mine, check that out.

(The EGR gas temp sensor is sorta designed to catch that; if the exhaust can't flow at all the temperature shouldn't come up enough. But who knows?)

mbomberz1

Thanks for the insight there scope, and the link! that is a great find. Will run through this over the weekend and report back.

Robert m

iTrader: (2)

why are you running 91?

mbomberz1

Because i was running my timing advanced

Gamefreakgc

Food for thought:


http://personal.utulsa.edu/~nathan-b...72systempu.pdf


Just confirms what scope said. Last ditch effort could be to get a new cat but no guarentees that'll work.

Gevo

Yeap, nearly the same problem with mine.

I spend a lot of time cleaning the plenum. It is NOT easy, I'd suggest going to the store and picking up one of those long round wire brushes that is also somewhat flexible and a lot of heavy solvent. I think it helped me a lot to eventually let her sit in a tub of solvent and I believe that helped the process.

Sturmcrow

When I got my truck it would throw a CEL at highway speeds with the code coming out to be the EGR temperature sensor. I tried a bunch of different things, including a new modulator, and none of them worked. In desperation I started blowing through vacuum hoses to make sure they were all clear. It turned out that the tube running from the EGR modulator to the EGR valve was completely blocked. Even though the modulator was working, it was not actuating the EGR valve itself.

I was able to clean the gunk out with a drill bit in about 20 seconds. No CEL since then. I also need to go in for smog in the near future for the first time with my truck. I am hoping that all goes well.

oldblue

if your factory cat was replaced with an aftermarket cat, i'd say thats the problem. aftermarket cats dont last long. i have a magnaflow cat i only put on for inspection, then take it off and put the other magnaflow cat on i replaced the factory one with a few years back. after one year of driving, i couldn't pass with it, and nox was why i was failing. so, i have one cat i keep on it for driving, and one cat for inspections only.

mbomberz1

Oldblue, what were your Nox numbers compared to your others? Relative to how bad each was. Just curious if your numbers looked similar to mine all around or if maybe the spread was not as far as mine between what passed and what didnt.


So today I went through and checked out the whole EGR system, step by step according to the PDF of the Toyota Manual that Scope was kind enough to link. Good or bad, everything checked out just fine. Good that I don't need to replace any of those parts but I was really hoping it would just be a clean out of the EGR or Plenum that would fix the issue. Upon taking out the EGR tube from the plenum and inspecting it, it was black like you would expect but there was almost no buildup of anything on it, or any of the internal piping in the rest of the EGR. Just a bit oily and black. Kind of disappointed!


Scope, I didnt remove the entire plenum as the EGR tube that goes in there didnt seem bad enough to warrant the job. So im not sure what the interal passage way that the EGR gasses take once released from the end of that pipe. Is there a complex or pathway or anything else that you imagine would still be clogged even if that pipe came out buildup free?

If there is no EGR issue, what does this leave me with?

• Just the Cat?
• Maybe O2 sensor, even though mine is only 10k miles old if that, i don't believe it is a Denso, if that would really matter.
• Could lack of adequate back pressure from my headers really be causing all of this? I had read some people thinking this was part of the issue but having a hard time believe it..
• My friend was suggesting I check the Fuel pressure to make sure its not running lean at all and causing the high temps, creating NOx. I didnt have time to test this today, but wanted to ask if this is a direction I should check as well.
  
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  Edit:
  
  Interesting thought, could air in my coolant lines cause High NOx somehow? I have had a water noise when my heater is open for quite a while, gushing kind of when i accelerate. I dont have any probs with the Coolant temp sensor i dont believe as the truck warms up properly, but maybe there is something else this could be affecting? Im not familiar enough with the more complex workings to be confident that its not an issue at all.. just thought I would throw that out there.

rworegon

Since the early 80's, cats affect NOx.

A three-way catalytic converter does three things:

1. http://en.wikipedia.org/wiki/Redox of nitrogen oxides to http://en.wikipedia.org/wiki/Nitrogen and http://en.wikipedia.org/wiki/Oxygen: 2NOx → xO2 + N2
2. http://en.wikipedia.org/wiki/Redox of carbon monoxide to carbon dioxide: 2CO + O2 → 2CO2
3. Oxidation of unburnt hydrocarbons (HC) to carbon dioxide and http://en.wikipedia.org/wiki/Water: CxH2x+2 + [(3x+1)/2]O2 → xCO2 + (x+1)H2O.

Older two-way (or "oxidation") catalytic converter does two things:

1. http://en.wikipedia.org/wiki/Oxidation of http://en.wikipedia.org/wiki/Carbon_monoxide to http://en.wikipedia.org/wiki/Carbon_dioxide: 2CO + O2 → 2CO2
2. Oxidation of http://en.wikipedia.org/wiki/Unburned_hydrocarbon (unburnt and partially burnt fuel) to carbon dioxide and http://en.wikipedia.org/wiki/Water: CxH2x+2 + [(3x+1)/2] O2 → xCO2 + (x+1) H2O (a combustion reaction)

Source: http://en.wikipedia.org/wiki/Catalyt...verter#Two-way
http://www.cchem.berkeley.edu/molsim...bkgcatcon.html

skypilot

iTrader: (1)

Have you tried backing off the timing and switching to 87 octane? It could be the slower nature of 91 that is causing this.

mbomberz1

Well the Cat theory just seems hard to believe, when looking at other peoples numbers my Cat comes up within range of a good functional cat on the HC and CO numbers, just missing the NO by a lot more than a good running 3vze.

Here is an example from a member here, Punchy:

See how high his HC and CO are with the bad cat? Mine are like his new cat. I imagine if my cat were breaking down, my numbers across the board would be high not just NO.

For the last two tests my Timing was lowered to 9 degrees advanced, 1 degree lower than Spec, so this shouldn't be the issue. From what i read i could possibly lower it to 8 and get away with it, but they would fail me for it being any lower than 8. The 91 im not sure, I cant imagine it would make it burn hotter.

oldblue

i passed hc and co but still failed nox. my numbers were very similar to yours

abecedarian

So, you pass low speed NOx and fail high speed?

Either your ignition timing is wrong or there's an issue with the EGU valve, and I suspect the first... though it's possible the fuel mixture is just a tad lean or your valve clearances are set too tight or cam timing is wrong.


But don't quote me on it.

Terrys87

iTrader: (1)

I have gotten several EGRs working. The carbon can get rock hard. I am not familiar with the 3.0 EGR but it is similar to the 22re. I feel you may need to pull the plenum as well and give it a good cleaning. All of the tubes will likely be clogged as well. The tube on the EGR and inside the EGR will have alot of carbon.

Here is how I clean mine.
Copied...
I worked on the EGR. Here is another picture that may look like the wrong way to do this, but the screw will strip if you use a screwdriver. Get a good firm grip, but not so hard to distort the screw.


With the screw out, get another bite on the the pipe to get it out of the EGR. Leave the carbon in the pipe at this time as it will help keep the pipe round. The carbon is hard as concrete. Slowly work back and forth to get the pipe spinning inside the EGR tube and to start breaking it free. Could take up to 10 minutes but just be patient.


Once you get the little pipe out, I tap on the the big nut with a wrench to help break the rust up on the threads. The I mount the nut in a vise and tap in both directions, tightening and loosening, with a rubber hammer. I have tried using wrenches and did snap an EGRs threads one time which ruined it. These run about $150 on ebay if I recall right. This could take another 10 minutes.

After it is apart, I use a drill bit, screw driver, nail, clothes hanger to get all of the carbon out. It is rock solid in places. You can put vacuum on the hose and see and hear the plunger moving and operating inside the EGR, the goldish part.

It is clean and working but didnt get any pics.


Here is one of the metal pipes that was clogged. The carbon gets hard as a rock. I use a drill bit with my fingers to help break it loose. The carbon on my finger is only half what came out of the pipe.


This is the same port that was clogged. The rest were clogged just as well. This is normal as to what you are going to find on a 150k mile or more trucks.

mbomberz1

Small Update,

Thanks Terry for posting your very helpful writeup on how you cleaned out the EGR. Over this last weekend i spend quite a bit of time pulling stuff apart. Pulled the Plenum and spent several hours cleaning it as best as I could. Let is sit overnight with some GUNK all over it, didnt do too much. Carb cleaner and elbo grease worked the best. Its real clean inside, about as best as i think you can get with out knocking out the plugs and dipping it in a tank of something nasty.

The EGR itself.. it just doesnt seem to be gunked up.. I pulled it off again, and tried to follow your instructions Terry. Got screw out from the Tube ok, but really had a hard time pulling the tube out. Was quite afraid i was going to crush the tube if i went any farther. Blowing through the tube has a very clear, non-clogged feel. No real effort to speak of, same with the top vacuum line, I can actuate the valve fairly easily creating a small vacuum with my mouth. What i did end up doing is the EGR tube that goes into the plenum, i soaked that in Easy Off, thing looks brand new. For whatever its worth, maybe that will help with the EGR gas flow a bit. I was afraid to try and dip the EGR casting in anything or spray too much stuff on it in fear that i might mess up the valve itself, since it seems to be working fine, and passes all of the FSM tests just fine.

While i had it apart, i took the general advice around here and replaced the PCV valve and gromit. What a pain, ended up having to remove the valve cover so i wouldn't lose some of the old hard gromit bits into there.

Since i had the one valve cover off, and the other has been slightly leaking, i went ahead and got new gaskets for them both and cleaned them up and re-installed them. Put everything back together, Started right up. And wouldn't you know it, my passenger valve cover is leaking 30 seconds later. I guess i didnt put enough RTV in there, or messed up the Torque.. I dont have a torque wrench that goes anywhere near 4FT lbs, so I went by feel. Looks like i will be getting a light weight torque wrench, and pulling it all off again this weekend.

Some possible good news here, I found that when i replaced my o2 sensor a few years back, it was a BOSCH. I had no idea at the time that these were not recommended. Its been running good but after the 10th comment i read about Bosch o2 sensors not playing nice with the toyota computers, i got a Denso to replace it with. No idea if it will help but I think this might be a missing key here.

Once the valve covers are not leaking and its all back together, I am planning on seafoaming through the brake booster, then installing the new o2 sensor. Also decided now was as good a time as any to flush out all the old coolant and finally put some toyota red in there, its been green ever since iv had it. New OEM plugs, cap and rotor too! why not.

OldBlue, not trying to avoid your advice here, just really trying to make sure all other things are crossed off the list first as I would really like to not replace that cat again! I think once this current list of things has been buttoned up and if I still am not running a lot lower, cat will be next.

Do you guys have any advice on how to make an aluminum cast Plenum shine like new with out sending it out? The top of it is pretty discolored and crappy looking.

jgrant721

mbomberz1,

I had a similar experience with smog testing on my '91 4Runner 3VZ-E and like you, just about pulled all my hair out trying everything I could think of to fix it. Since we are both running the Thorley headers which I believe were at least partly responsible for the problem, my solution may work for you.

It turns out that something about the hi-flow Thorley headers and or the Magnaflow CAT affected the operation of the EGR VSV so that it was not doing it's thing during the smog test. The solution was, for the smog test, simply unplug the connector on the EGR VSV (the green vacuum valve at the front of the group of three mounted on the passenger wheel arch in the engine compartment). That was the only change I made to get me from a series of failures to a regular pass.

You can read all the details in the post:

https://www.yotatech.com/forums/f116...estions-260138

Post #25 has the test results

Hope it helps!

Jim G.