FourEyes

Hello Fellow 1st Gen Enthusiasts,
Up to now I have always been able to find answers to my truck questions by searching the forum (thanks everyone!) but it has finally come to the point where I need to ask a question of my own.
That said, this is the first thread I've started so please let me know if there is anything I should do differently.

To the point,
My truck is failing smog with high NOx and I have been beating my head against the wall for months trying to get it to pass. I'll save you the long story and grimy details. Listed below are the particulars of interest.

Truck:
1983 SR5 Longbed 4WD

Parts of note:
- Rebuilt 22r from Yota 1 Performance in Modesto CA with approximately 6000 miles on it
- Light port/polish done to intake and head
- Stock cam
- Rebuilt Aisin carb from Recarbco in Martinez CA
- Stock air intake
- LCE street header with air injection and O2 sensor
- Custom 2” stainless exhaust (no leaks of consequence)
- Brand new Magnaflow catalytic converter and muffler
- New cooling system that seems to be functioning perfectly
- Brand new Toyota EGR valve / new Toyota BVSV (EGR modulator is not new)
- New LCE pro distributor / cap
- New coil and ignitor
- New plugs / newish wires
- New smog pump and functional EACV
- New fuel pump and lines
- Fresh oil and filter

Settings of note:
- Timing set correctly (5 degrees with advance cut / advances to first unnumbered mark with advance)
- Compression is a bit high. In the range of 185 – 194 across all cylinders
- Does not appear to have a vacuum leak (tested with propane)
- Fuel looks good in sight glass
- Running on 91 octane

Tests:

Before new cat, EACV, exhaust, and EGR:

%CO2: 15mph MEAS: 14.0 25mph MEAS: 13.1
%O2: 15mph MEAS: 1.2 25mph MEAS: 2.8
HC(ppm): 15mph MAX: 150 MEAS:122 25mph: MAX:130 MEAS: 64
CO(%): 15mph MAX: 1.56 MEAS: 0.68 25mph: MAX:1.36 MEAS: 0.06
NO(ppm): 15mph MAX: 1060 MEAS: 2046 25mph: MAX: 962 MEAS: 2919


After the new catalytic converter:

%CO2: 15mph MEAS: 16.2 25mph MEAS: 13.3
%O2: 15mph MEAS: 0.1 25mph MEAS: 2.9
HC(ppm): 15mph MAX: 150 MEAS:105 25mph: MAX:130 MEAS: 23
CO(%): 15mph MAX: 1.56 MEAS: 0.07 25mph: MAX:1.36 MEAS: 0.00
NO(ppm): 15mph MAX: 1060 MEAS: 100 25mph: MAX: 962 MEAS: 2186

After the new catalytic converter and EACV:

%CO2: 15mph MEAS: 15.5 25mph MEAS: 13.6
%O2: 15mph MEAS: 0.8 25mph MEAS: 2.4
HC(ppm): 15mph MAX: 150 MEAS: 34 25mph: MAX:130 MEAS: 21
CO(%): 15mph MAX: 1.56 MEAS: 0.01 25mph: MAX:1.36 MEAS: 0.01
NO(ppm): 15mph MAX: 1060 MEAS: 733 25mph: MAX: 962 MEAS: 2355

After this the smog place stopped giving me print outs (haha) and just ran it in the machine. So the only numbers I have are only the NOx by memory.


After new catalytic converter, EACV, and new exhaust (old one was leaking pretty badly):

NOx: approx 2800 at 25mph (Worse I know! I think this is because without leaks it's all coming out the back now)


After new catalytic converter, EACV , exhaust, and EGR:

NOx: approx 1150 at 15mph and approx 1350 at 25mph (much better but not there yet)


At this point I have gone through everything I can think of to bring the NOx down. If any of you awesome Toyota lovers out there can shed some light on this for me I would be so very very appreciative. I was planning a wheeling trip with some friends for the beginning of the new year but looks as if that isn't gonna happen anymore.

Please let me know if I have left out any pertinent information.

Thanks in advance for your time and mental exertion.


Regards,

Sam

P.S. Because I know everyone loves a picture, here are some of the truck in question:

Punjab

Sorry to hear about your troubles! Your truck looks clean and that motor is mint. I wish I could be of more help. I actually just went through emissions with my truck, which is heavily modified by comparison, in Colorado. In years past I was able to tune it to pass on my own but for some reason this year I was having a hell of a time with it.
So, I just bit the bullet and took it to a shop with a dyno. They tuned it, took it to emissions for me and passed, wrote down what they did, and then were kind enough to tune it back to make power for me.

If you have to pass and re-pass every year it might help if you can find someone that tunes carburetors and has an emissions tester just to give you base line settings.

FourEyes

Punjab,

Thanks for your kind words. You have helped with your support, your experience, and your good advice. The picture of the motor is from shortly after I dropped it in and it was still getting broken in. After a few wheeling trips it's not so mint anymore but, it's the good kind of dirty. HaHa. Yeah, I wish I could do more modifications engine wise but California is such a pain when it comes to emissions. The shop you took it to sounds awesome! As much as I hate having someone else put their hands in my truck, I have reached the point where I have started to look around for shops to do some diagnoses and tuning. There's just not many around that want to do that for a 22r without breaking the bank..

Thanks again,

Sam

FourEyes

Anyone else out there have any ideas?

dropzone

iTrader: (6)

Have you done anything with the EGR?

toyospearo

I have worked on quite a few california carbed Toyotas over the years. A lot of those were rigs someone brought me to bring back to life. Most pulled out of fields or had been sitting forever. The smog was always the challenge. And I don't remember any ever not passing some maybe on the second try. I always made sure to start at the cat and work forward. Making sure everything was either functioning or replaced. I do remember if there were high nitrogen oxide readings its as because the carb was leaned out or the timing was off. I have heard a few tips and tricks to give you better chances of passing if you are on the borderline. One was making sure the oil was just changed. I have heard people using straight Ethanol. Expensive but worth it if you are having smog headaches. Like Dropzone said check the EGR. That could cause higher cylinder temps. The egr DOES reduce NO out the tail pipe.
Check this dude out.. Listen closely around 12:13

FourEyes

Thanks for your replies!

Dropzone,

I replaced the EGR with a brand new Toyota one and appears to be functioning properly (not a cheap part unfortunately). It did help but not enough to pass (see first post, last smog results).
The rest of the parts that have been replaced or are relevant are listed in my first post.


toyospearo,

Yeah, I tried to follow the same logic. As you can see from the lists in my first post, by now I have replaced pretty much every part relevant to NOx (at least that I can think of). Not sure how a shade tree mechanic like myself can really diagnose a lean carb condition besides reading plugs. Any tips? Last time I looked the plugs looked good. I'll check again. Timing is spot on and advance is working properly. The last test was about 30 miles after doing a fresh oil change. Thanks for the video, nothing I hadn't learned by now (read the FSM waaaay too many times haha) but very nicely explained and gave me an idea of something to check. I'll save that one for sure.

The truck passed with flying colors when I bought it so I'm thinking it has something to do with my engine swap or something broke. Both definite possibilities. I'm beginning to suspect the EGR Modulator. It is difficult to test accurately (as per FSM).
Unfortunately, this style modulator seems impossible to find new. I'm also going to do my 1000th vacuum leak test, this time with smoke.

Thanks again for your replies,

Sam

toyospearo

We are lucky up where I live in CA. We only have to smog ONE TIME!
Take a pic of the egr modulator and send it to me. I bet we have a few laying around. Not super common those fail but it happens. Take a picture of one of your plugs as well. Might richen the carb up a one turn. Looks like you done about everything. Can't hurt at this point to swap out that modulator.

FourEyes

Oh man, If only! We gotta do it every two years down here. Awesome! Thanks! I'll snap a pic of it tomorrow. Yeah, didn't seem like it was very prone to failure but can't hurt to try another. I'll check the plugs again tomorrow as well.

Thanks again!

Sam

Yotard

Putting the cat on artificially lowered your numbers and will ruin that cat pretty quickly. I put your numbers into the smog lambda call before you did anything and you have a lambda of 1.145. You will never pass smog unless you are between .940 and 1.020. You are running so lean you are going to destroy that engine. Get that carb professionally tuned. You most likely need to put different jets in it. Talk to yota1 that have a great smog tech there.

13Swords

In my experience, high NOX results from a lean condition. Have you pulled your spark plugs & checked the color of them to see if the engine is lean, rich or normal? "Not new" EGR Modulator may not be doing the job right, allowing in too much exhaust gas, leaning it out. Did your carb rebuilder use the stock jet sizes? How many turns out is your mixture set? Should be 1 & 3/4 turns out. Pull the vac line to the AAP (Auxiliary Acceleration Pump) & check for gas. The AAP adds a little gas to the mixture when the engine is below normal operating temp. The AAP is on the passenger side of the carb, three screws holding the cover on. If you find gas in the vac line or port on the cover, the diaphragm is ruptured, or your carb builder didn't put the diaphragm in the right way. That can also throw off the mixture, even when the engine is warmed up.

Why the 91 octane? Higher octane gas burns slower, so you may be getting an incomplete burn.

Yotard

It's really lean

FourEyes

So here are some pictures of my plugs:

I've been working on motorized vehicles for a bit now but I still suck at reading plugs HaHa. What do you guys think?







Yotard,

Yeah I ran it through the Lambda the other day (just learned about it) as well have been concerned about damage so the truck has been parked. That cat did seem to lower the 15mph but not the 25mph much so I had assumed it was artificial. The only component change that actually did much was the new EGR. Yeah I'd like to have the carb tuned just gotta find the right place (and the money haha). Didn't know Yota1 had a smog tech. Good to know, I'll give them a call. Thanks! The interesting thing is that this carb came from the place that Yota1 gets their carbs. I would think that it should already be tuned pretty well for this engine. They even test the carbs on an engine before they sell them to ya.

13Swords,

I assume they used stock jet sizes but haven't actually checked. By mixture screw I assume you mean the Idle Mixture Screw? If so, the FSM says to start at 4 turns out as a baseline then to tune it using the lean drop method. Mine is a 5 5/8 turns out (as per the carb builder's settings) which in my understanding puts it a little bit on the richer side from the FSM starting point. The AAP vac line did have a whiff of gas about it but no actual liquid fuel in there like I've seen in the past when they really go out, wadda ya think? I'm running 91 for a few reasons. Firstly, the truck just seems to like it better. I assumed it was because of the now higher compression with the rebuild. Also, yeah the 91 does burn slower but it also burns cooler. With the NOx most likely being caused by high combustion temps this should theoretically help a little bit. These are all based on my limited understanding of octane ratings and some internet reading though.

Thanks for your replies,

Sam

FourEyes

toyospearo,

Here are some pictures of that modulator.





Thanks,

Sam

Yotard

Dude the lambda doesn't lie. You are way too lean and that's what is causing your NOX problem. The best thing to do it put an o2 sensor and a gauge on it so that you can make sure it's staying at 14.7:1 air to fuel ratio when you are cruising and 12:1 when you go wide open. Right now your air fuel is saying you are running a lambda of 1.145 x 14.7 = 16.8 air fuel ratio at 25 mph. That is dangerously lean! And completely the reason you are failing smog

FourEyes

Oh yeah, I believe it for sure. That's why I immediately stopped driving the truck when I saw those numbers the other day. I learned about the lambda from a different yotatech thread just a few days ago. Wish I had learned about it much sooner. It just seems odd that the carb settings would be so drastically off. Do think a vac leak could make it that lean? Checked it before but gonna check yet again today with smoke. One other interesting thing that I forgot to mention is that when I did a test of the O2 sensor a while ago it was pegged at the .7 side of the scale and not switching at all. Doesn't that mean rich? It's a brand new sensor.

Thanks Yotard for your advice,

Sam

Yotard

I don't know... usually when a sensor is pegged and it's brand new something isn't hooked up right. Toyota's are switched ground and so it can be a little different to wire these gauges. Most of the time they include the wiring for both switched ground and switched power.

I'm doubtful that it's an exhaust leak. Carbs have a best guess out of the box setting but it's got to be tuned to the engine that it's mated to with that intake and all.

northoak

toyospearo

let me see if I can find one of those modulators around. I'll get back to you mid week.

13Swords

Your plugs look generally ok to me, just a bit darker than I ideally like to see them. Mine is dialed in pretty good & I get a light tan color.

I'd double check on the jet sizes they used, just so I could know for sure what I'm dealing with. Yes I did mean the Idle Mixture Screw. If the FSM says start with 4 turns I'm not gonna argue. Question is though, how does she run at that 4 turns out setting? OK? Did you try doing the "lean drop" adjustment, running it in until you get a lil misfire, then backing it out until it was good? Just curious.

AAP. No liquid gas is good. Plus your #1 plug isn't showing any fouling or signs of being real rich, which is where a leaking AAP diaphragm would show up. Channels gas straight to #1 cylinder usually.

You're right about the higher octane slow burn being cooler, & I get that if the truck likes it better you should probably do it. Mine runs better on 89 Non-Ethanol over the 87 10% Ethanol.

Keep at it boss, you'll get it solved I'm sure.