dr1553

Just failed emissions on high speed NOx (25mph @ 1,946RPM), reading 1062pm, standard is 956.

This is the first time to get it inspected since Aug 2010. I haven't been driving it but I have made sure to start it every few weeks and run it up and down the driveway. Only put 2,300 miles in 4 yrs on it.

I know the idle valve in the TB is stuck open or not sealing for some reason. Will this cause a high NOx reading? I'm thinking it will cause the engine to run lean when warm because air is bypassing the butterfly valve? Engine does not compensate for that extra air by adding more fuel because it only goes by how far open the butterfly valve is open thru the TPS?

Had high idle (1700rpm) when warm, adjusting idle screw on TB brings idle down even when warm. I removed the TB and cleaned it out and was able to pull the idle valve closed so I know it will move but not sure if its moving with coolant temp like it should.

I only get one free recheck so don't really want to blow it.....I'm thinking of just blocking the port off in the throttle body and seeing how it runs. May be harder to start when cold I'm guessing? But it never gets cold where I live.

I will pull the spark plugs once the engine cools off to see if they look lean. The tailpipe is dry and zero soot inside....squeeky clean. Should be a little soot in there huh? Kinda confirms lean. Also engine has zero power and has slightly rough idle.....can just tell something isn't right.

I will check the EGR system, I know I had to replace the EGR valve modulator to get it to pass last time. I know it was working correctly then, but that's been 4 yrs ago now. I will also do a good search for vacuum leaks with a propane torch.

Just wondering if the stuck idle valve in the TB could for sure be the culprit.....or probably not.

HC was 48, standard is 151.....CO was 0.10, standard is 1.68

scope103

That's a really high NOx number; average passing NOx in California is 53ppm.

So concentrate on your EGR system. That's its job. That's its only job. Pull the tube that enters the plenum. At the vintage of your vehicle, many of us have found the plenum filled with 'crud,' enough of which will block the tube. Run all the diagnostics on the EGR system. http://personal.utulsa.edu/~nathan-b...77exhaustg.pdf

I doubt it has anything to do with the idle valve. The mixture is determined using the airflow determined by the VAF, not the TPS, so add'l air bypassing the throttle plate still goes through the VAF. A very lean condition can raise combustion temps, which will raise NOx, but not as much as you're seeing. And a very lean condition would throw a code. (I assume you've already checked for codes, particularly 71.)

Good luck!

dr1553

Thanks Scope....I'll print those pages and run thru them tomorrow.

I think the EGR is opening because the tube does get warm....but maybe its not opening at the right times. It should be closed at idle and open at steady speed right?

I do remember taking it apart and cleaning it out last inspection time....plus changing the modulator. I don't remember checking the VSV....so I'll for sure try that.

I did replace the O2 sensor, cat and new muffler last inspection time too. It was almost 4 yrs ago but only 2,300 miles ago.

No codes are showing or stored. I did get the knock sensor error some time back (52) but nothing today. I drove it more miles today (maybe 30 total) than I have in yrs.

So with that high of a NOx I should for sure concentrate on the EGR system first huh? Nothing else it really could be with NOx that high?

dr1553

Just for fun warmed the truck up and applied vacuum directly to the EGR valve to see if the valve was at least opening....yup....engine stumbled and tube warmed up instantly.

So now to find out if the EGR valve is ever getting vacuum from the engine to open the thing while running.

Also found this thread.....

https://www.yotatech.com/forums/f116...-calif-222662/

So by unplugging the VSV was he insuring the EGR valve would stay open while running at 3,500 RPM? I'm guessing the VSV will stop vacuum to close the EGR valve if engine is under load or whatever situation it is that makes it close for more power?

So if my EGR is staying closed that would explain the high NOx but not the crappy idle and what seems like an absolute dog of an engine. No power and terrible mileage. Seems like more of the common stuff would cause HC fail....coolant temp sensor comes to mind.

Could be valves clearance too tight but that would fail HC for sure?

I'm ready to get into older vehicles.....carbs and points for me please. That's why I spend my miles on my '77 KZ1000 and not in the 4runner.

I'll run the other EGR tests tomorrow and see what I come up with. First thing first.....get the NOx under control. I bet I either have a restricted vacuum line/tube or the VSV is bad.

mbomberz1

I just went through this same ordeal on my truck, nox was over 1k to start, down to 22 now after a bunch of work. Check out the thread and see if any of it helps you out.

https://www.yotatech.com/forums/f116...-blues-279932/

I did a bunch of changes between my 3rd and 4th smog test, it dropped from ~700 to 22 then, so i cant say exactly what helped the most, but i believe you should clean out your plenum and egr, mine tested fine like yours. Also i put in a Denso o2 sensor, had a bosch which might not have been helping my cause. Hopefully my thread can help you out.

dr1553

Did the tests and no vacuum to the EGR...started tracing it back and found the tube going into the VSV completely plugged with rust dust. The tube that runs along the plenum is rusted inside. Looks like I'll be running a soft vacuum tube from the VSV to the EGR valve and bypass the hard tubing.

I'm going to pull the VSV off and see if I can get it cleaned out and working.....if not.....what is the P/N for the VSV? I'm having trouble finding it and my local dealer didn't know what I was talking about.

blake.nemitz

a few years ago mine failed 5 times in a row with high nox. I ran it at zero degrees timing and passed. it will be gutless but might pass, mine did with drastically lower nox numbers.

dr1553

Got the VSV cleaned out and working....could tell EGR valve was now opening by the difference in how it is running, verified with vacuum gauge.

Took it back and it passed....guy testing it said it is running much better....I thought it was even more gutless than before on the drive over. I think a '91 Geo Metro with a dead cylinder would smoke me.

Maybe its time for a knock sensor replacement...it has thrown code 52 before a few times.

So it passed but NOx was still a touch over 500ppm. How in the world could some be getting under 100? The standard is 956 so that's WELL under!

I do have an NGK o2 sensor from sparkplugs.com (24111) I installed in 2008. A cat and TPS I bought from O'reilly in 2010. Had a new muffler installed same time as I put in the cat...I dunno what brand it was...just from the local muffler shop.

I know all these parts are from yrs ago but they have under 4,000 miles on them. The cat, TPS and muffler only have 2,500 miles on them.

The guy at the inspection shop said he would run a "practice" emissions test for me anytime for $15. So I can make changes and see what happens.

For future reference the EGR VSV P/N is 90910-12075, number is printed on the side of it. My local dealer wants $174.51 for one, that's $20 over MSRP....nuts.

Terrys87

iTrader: (1)

Ever EGR I have ever worked on I have been abloe to get working, but I dont have to deal with smog test but I think it would pass if I needed it too. Just needs a good cleaning. Here is another link https://www.yotatech.com/forums/f116...-blues-279932/

It is for a 22re motor but most still applies for you. Glad to see you passed.

dr1553

I pulled the intake plenum off in 2006 or 2007 to seal up leaky valve cover gaskets. I remember cleaning it out but I also remember that it wasn't that dirty.

Where does all the crud build up that you guys are talking about?

Next time I pull my intake plenum I'm going to go further and check/shim valves, change coolant temp sensor, replace all the vacuum tubes, probably pull the lower intake and install new knock sensor and wire....might as well do all that once the plenum is off.

I only have to pass emissions testing once more....25yrs + old in Texas = no more emissions testing! But I still want to keep it running clean.....not planning on disabling emissions parts on the engine just because I can.

scope103

I am glad to hear that every time someone says it. It would be one thing if disabling emissions gear resulted in huge performance improvements (it doesn't). But the explanation I hear the most is a desire to "clean up" the engine compartment, as though the writer was a loony interior decorator.
The plenum gets oil-blow by through the PCV, carbon (unburned fuel during the few moments of running rich) through the EGR, fuel through the evap system, and very fine dust that makes it through the induction system. All extremely tiny amounts, but 20 years or 300,000 miles is a long time. I can't prove that any of these things are the sources, but the "crud" I had was consistent with any of these.

And given the tiny amounts I'm thinking of, it wouldn't surprise me if others had a different experience; perhaps you use a slightly better grade of fuel, or you live in a wetter climate (less air-borne dust). Who knows?

dr1553

Yup...the two biggies are the EGR and the PAIR. From recent reading the PAIR just takes some clean air from the intake and puts it into the exhaust.....don't see how that can hurt performance.

The EGR seems to be much more controversial. I will agree that dumping spent exhaust back into the intake doesn't sound good for a few reasons. But it does lower combustion temps and I think on the 3.0 that's a good thing. With our frail head gaskets, hot #6 cylinder and all.

I was wondering where in the plenum the crud builds up? Where do I need to look next time I have it off? Is it on the passenger side where the EGR goes into it? That area?

Do you have any suggestions on the knock sensor? I think this may be a possible source for a lot of my problems. No power....poor mileage....slightly rough idle....timing mark jumps around when looking with light....that kinda stuff. Especially since it's thrown code 52 a few times.

I was thinking of just buying a new knock sensor and wire from Toyota and installing it in the driver side rear lifting hook. Just to see what happens....if it runs much better and doesn't throw the code anymore great! If not I'll at least have a good one to install when I pull the intake eventually for some reason. I found the P/N for the wire (82219-35010) but I cannot find the P/N for the sensor itself.....does anyone have it?

Also...is there good source for finding part numbers online?

nuttytowle

hay man new to this sight but try denatured alcohol. go with a 3-1 mix of gas to alcohol. worked on my buddies 240...it actually failed the first time cause we used 100 % alcohol. it was so good it didn't even read. so we had to do it again. we used 1 gallon of alcohol -3 gallons of gas. this trick has also worked on a Honda accord, a 318 small block and an sr20, but i am sure it will work for your truck.

pplusent

Found an emissions trick for the 4 runner 3.0, talked to a guy who has been running a smog repair place for 40 years. As the 4runner ages the EGR can't add enough exhaust to bring NOX down to good levels. He has found that there is a restricter in the EGR valve. If you look inside the EGR valve you will see what looks like a freeze plug with a hole in it, remove the plug and the EGR will bring the NOX down to good levels. Hope that helps.