Failed emissions testing

[gws34]

You're almost there!

Drop your main jet down to #48.
Verify that your EGR valve is opening correctly within the parameters. Is it connected to port vacuum? Is the PVS opening properly?

Check for any vacuum leaks at the carb base plate & EGR connection.

After setting your main jet. Set timing to 8-10 degrees, and set the idle mixture using the vacuum gauge. Once you have relatively smooth vacuum, turn the screws in a 1/2 turn. Ignore the 'timing to low' zone on the vacuum gauge (if it has one).

The truck should run fine (unless you have an outrageous cam).

Speaking of, stock cam?

Stock cam, that I am aware of.
I have ordered 46 and 48 jets was actually considering jumping all the way down to 46, would you recommend 48 to start with, Guess I don't want to jump to far down

Is setting the timing more advanced going to help? I believe stock setting is 6 degrees

EGR is brand new-should be working properly

 

[gws34]

I've been fighting the Pima Co. Az. emissions since about 1980. At first, I went to the test and of course failed. Then I went to one of the emissions shops to get charged 50 bucks and a bunch of vacuum leaks. Then I passed and went back to the emission shop to get the truck running again. By then I knew the whole thing was a joke. Later, a friend with a shop and a 3 gas analyzer let me play. I found you can lean the mixture and the CO goes down and hydrocarbons go up. At one point both are low enough to pass. Without the analyzer, it's hard to tell the desired A/F ratio. The sleazy shops just speed up the curb idle to about 1200 RPM and pull hoses to create vacuum leaks. By now the engine is shaking, but will pass. What a scam. They don't even try to find the A/F ratio sweet spot. You need an honest shop that makes an effort to do it right.
The emissions check stations don't know exactly what you're supposed to have. I pulled the air pump on one EB and changed the alt. bracket. They didn't notice, but when I previously simply left the belt off I failed for equipment on the same truck. My '77 never had air injection from the factory. They never mentioned it. I'm sure EGR and cats. are the same. If it looks like it's there and hooked up you're OK.
Your results look to be mostly idle related. Different jets won't help that.

Why is it an idle thing and the jets won't help. If Idle is set at 550 (stock) and timing is set at 6BTDC (stock) where is it that it is an idle thing? What else can I adjust without leaning out the mix and dropping vacuum?

 

[tirewater]

(odd, I thought I had responded, so hopefully this isn't a double post)

Go with #48 (which was stock for some years). Too lean will generate more NOX.

If my memory is correct, the PVS for the EGR valve is set at 145 degrees F. So the EGR valve should be opened when the vehicle is warmed up and idling.

If you have timing leeway in the test, I'd set it to the upper bounds of 8. This will generate more vacuum, which you'll need to open the EGR valve.

I failed my last smog with higher co2 & higher nox readings as well. Turns out I had swapped in #52 jets to see how the truck would run, and I never got around to swapping back. I used #48 jet, and passed.

Stock cam, that I am aware of.
I have ordered 46 and 48 jets was actually considering jumping all the way down to 46, would you recommend 48 to start with, Guess I don't want to jump to far down

Is setting the timing more advanced going to help? I believe stock setting is 6 degrees

EGR is brand new-should be working properly

 

[EPB72]

GWS,, tirewater is making some good points .Lean mixtures,, advanced timing will create more nox ,,egr is to reduce nox in California we test with a 5 gas analyzer and nox is tested here as well as CO,HC,,,it appears AZ doesn't test nox.. Your cat.converter is to reduce CO and HC if working properly at 6+% CO your damaging your cat it"s life span will be short lived..

leaning out your mixture will eventually cause HC to elevate at some point lean even further then a lean misfire develops thats when you notice the rough running.....But lets say you lean down to 1.8-2.0 % that might actually start letting the CAT start working properly and reduce emissions more ,,,

So with a solid stockish motor timing 6-8btdc ,,34 -36 total timing,,,a well working properly tuned carb pre cat CO reading of .9-1.3 maybe a little higher, a working cat Post CAT reading should be very clean,,,had some as an example HC 33ppm CO .2

So in AZ you say loaded test what does that mean??? in Cal our loaded ASM test is on a dyno first at 15 mph within a RPM window and then 25 mph within a RPM window. generally both speeds in third gear ..

 

[jckkys]

The jets only effect fuel flow through the booster venturis just like the power valves. It's called the main circuit. The idle circuit is for both idle and transition. If the idle circuit id too lean larger jets or no jets won't change that. I remember the emissions test involved idle and 30-35 MPH on a chassis dyno. I don't know what you mean by loaded. The dyno is free wheeling with no resistance. If there were any resistance you'd just drive off of it. So there isn't any load.

 

[gws34]

The jets only effect fuel flow through the booster venturis just like the power valves. It's called the main circuit. The idle circuit is for both idle and transition. If the idle circuit id too lean larger jets or no jets won't change that. I remember the emissions test involved idle and 30-35 MPH on a chassis dyno. I don't know what you mean by loaded. The dyno is free wheeling with no resistance. If there were any resistance you'd just drive off of it. So there isn't any load.

Yes, the paperwork calls it loaded but yes it is on a dyno going 30-35 and then at idle.

 

[gws34]

(odd, I thought I had responded, so hopefully this isn't a double post)

Go with #48 (which was stock for some years). Too lean will generate more NOX.

If my memory is correct, the PVS for the EGR valve is set at 145 degrees F. So the EGR valve should be opened when the vehicle is warmed up and idling.

If you have timing leeway in the test, I'd set it to the upper bounds of 8. This will generate more vacuum, which you'll need to open the EGR valve.

I failed my last smog with higher co2 & higher nox readings as well. Turns out I had swapped in #52 jets to see how the truck would run, and I never got around to swapping back. I used #48 jet, and passed.

sorry it was meant to be a question, would 46 be better than 48 because it would let less fuel through?

I thought they tested for NOX also but it is not on my results, they might only put on the paperwork what i failed on, since nox would be low with a rich mix happening.

Thanks
Glen

 

[gws34]

What else can I do to the idle "circuit" to change or adjust things?

 

[EPB72]

The dyno is free wheeling with no resistance. If there were any resistance you'd just drive off of it. So there isn't any load.

In california the loaded asm test have resistance and it takes a bit of effort to be able to get the vehicle to drive off the dyno..the 15mph test is loaded to about 18% and the 25mph test loaded to about 25% plenty of load to get manifold vacuum below 8 in'..and well into the main metering circuits..

not sure about AZ test cant imagine they test it freewheeling there's got to be some load or it would be waste.

 

[Rustytruck]

What else can I do to the idle "circuit" to change or adjust things?

watch your float settings if set too high the transition circuit will come in too early as its is easier for the internal passages to pull fuel in early. check your power valve for leaks or the wrong one or leaking allowing extra fuel to come in too soon.

make sure your idle speed is no lower than the specifications on the emissions decal. low idle is a killer for emissions testing. they usually allow a higher idle which cheats the test but too high pulls too much fuel from the transition circuits.

use non alcohol fuel or Chevron gas for the tests. Chevron use to be the factory fuel for emissions testing for a very long time.

 

[welndmn]

Do you guys in AZ measure anything else?
If you had a O2, CO2, NOX reading as well it really helps pin point the issues.

 

[gws34]

Do you guys in AZ measure anything else?
If you had a O2, CO2, NOX reading as well it really helps pin point the issues.

I believe they measure all of the gasses, but the readout I got only shows what failed. Maybe they don't but that seems strange to me that they would not have all 5 gasses included. This is my first time in AZ dealing with this my other cars are newer and they just hook up the computer and do not use a sniffer.

 

[toddz69]

Do you guys in AZ measure anything else?
If you had a O2, CO2, NOX reading as well it really helps pin point the issues.

Our emissions testing here measures CO and NOx.

Todd Z.

 

[jckkys]

Today I did a deep research of Az. emissions tests and inspections. Both Pima and Maricopa Co.s have what they call Waiver/Referee Stations. The one in Tucson is on Business Center Dr. by Prince & I 10. It was the only place at either the DMV or ADEQ with an informed employee. The Maricopa stations are on Stocker Dr. and Renaissance Dr. The specs they go by come from the annual Mitchell Emissions Control Service & Repair Manual. They say you need a new one every year to keep up with EPA changes. The 2020 version is already out of print but costs $150. The earlier years are much cheaper on ebey, which seems OK since our EBs are about 50 yrs. old. The waiver referee said '75 302s only need air pumps. They don't even look for EGR. Of course a '75 still needs the tail pipe sniffer. The idle mixture screws can do what's needed by using a 3 gas analyzer to check the CO and NOx. They couldn't tell me the pass/fail for a specific yr./model. I did find out that the specs are tied to the engine and yr. not the chassis. So my '69 351 (the first yr. for 351s) doesn't need an air pump. Obviously any 351 is a '69 for my purpose. Because it's carbureted. So I put a '69 351 emissions sticker on the valve cover. It just has the idle speed and initial timing on it with a '69 part number. I don't know if the '75 351 has air injection. I recommend any Az. EB owner in the 2 covered counties call the the waiver/referee station with questions.

 

[WheelHorse]

Buy a wideband sensor, hook it up...to measure is to know. Install before cat!

My bronco actually idles like a kitten around low 12's on the afr gauge...that would not pass emissions. When I lean out to low 14's you can hear the cam chop a bit. Mine has an Edel performer cam.

Running the wideband I discovered the idle circuits only control...yup you guessed it...the idle. I ran 57 jets as a test. I could dial the idle in, but as soon as I got out of the idle circuit she ran pig rich into the low 11's without power valve actuating.

With the 2150, you can use a Holley power valve as well. I found my power valve opened really early causing slight tip in to be rich from my Walker kit. What do I mean by that...it was around 12" of vac she would go full rich. I was barely into the throttle and it was running low 12's afr. I stepped down to a 6.5" so now I have to be down to 6.5" of vac to have it go full rich and maintain around Stoi during normal acceleration. Hly-125-65 is the power valve I used.

 

[ntsqd]

I'm not sure that a wide-band will help with passing emissions, but it certainly will help make it run right afterwards.

 

[jckkys]

Passing emissions and making an engine run well are 2 different things. The immediate task is passing emissions. A 32 MPH light load is still in the idle circuit. It's hardly a fast idle. The main circuit isn't part of the equation, so jet size and power valve enrichment are irrelevant. I found that moving the accelerator to keep the speed between 30 and 35 messes with the A/F mixture when more fuel is added by the accelerator circuit. The trick is to keep the speed at about 32-33 while not moving the accelerator peddle. The movements produce a delayed response in MPH. With no load on the engine, the MPH changes a lot with a tiny movement of the accelerator. This is complicated by an automatic working through the gears. To be good at this practice is needed but you only get about half a minute. Then the tester will want to take over. Unfortunately they don't care you pass.

 

[phred]

I’m so glad I no longer have to deal with this nonsence after moving back to NC from OR. Both broncos where pre active emissions but still needed to pass the sniffer test. To pass I had to lean them both out to the point they would barely run. I’d pull up the the inspection station get out and lean the carb, nurse it into get sniffed, pass the test, pull back out and richen then back up. Testing pre-emissions vehicles in my opinion is just a money grab.


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[gws34]

UPDATE!!

It Finally Passed, with flying colors!

Replaced Carb jets down to size 46- Will probably bump them up to size 48 next week- Can feel it is sluggish on acceleration.

Found that one of the air pump check valves was not fully functioning. could not find the stock valve so had to modify a newer one, but it worked.

Thanks you all for the help.

Finally get to start driving it on the road.

thanks
Glen

 

[WheelHorse]

Glad you're going down the road!