Failed Emissions AZ

[brbuilder]

Looking for help to pass my emissions test in AZ.

HC 320 loaded reading/450 loaded standard - pass
HC 371 idle reading/450 idle standard - pass
CO 8.77 loaded reading/3.75 loaded standard - fail
CO 5.55 idle reading/5.00 idle standard - fail

Last year it passed -
HC 211/450 loaded
HC 373/450 idle
CO 2.11/3.75 loaded
CO 4.97/5.00 idle

Q-jet built by Bruce at Carbs Unlimited. Installed before last year’s test.
Idle set at 700rpm, 18”vac
Performer intake, headers, dual exhaust.
195 t-stat.
Also added a charcoal canister.

What would cause the CO to increase that much? Any suggestions?

 

[DirtDonk]

Bad, or different (?) PCV valve?
Fouling plugs?
Incorrectly plumbed charcoal canister?
Secondaries stuck open just a bit?
Vacuum leak?

Not even sure if any of those would change the CO, but they were the first things I thought of.

 

[DirtDonk]

Or hey. Just plug in an OBDII scanner and see what the computer says!

 

[dirtwheels]

Or you can get "Classic Car" Insurance in Arizona for your Bronco , show DMV proof and be done with the whole smog game .

 

[AZ73]

• Rich carburetor mixture (main jets too large, mixture screws set too rich).
• Choke stuck closed or not fully opening after warm-up.
• High float level in carb causing excess fuel.
• Restricted air filter limiting airflow.
• Weak spark (worn plugs, points, condenser, coil, or cap/rotor issues) → fuel not fully burned.
• Incorrect ignition timing (too retarded usually raises CO).
• Misfiring cylinder (unburned mixture increases CO/HC).
• Low engine temperature (bad thermostat keeps engine cool → choke on longer, mixture richer).
• Vacuum leaks in the wrong place (sometimes cause rich idle if carb compensates).
• PCV valve stuck closed → crankcase vapors not being re-burned, can richen idle mix.

My initial guess is your timing chain has stretched slightly causing a slightly retarded ignition timing, but that big of a difference isn't explained completely by that. I would double check your timing, clean your PVC valve, and honestly change your plugs. You run a choke so your plugs get dirty. Try a new air filter too.

 

[Broncobowsher]

Numbers show me a little rich. It could be an air bleed isn't clean and slightly restricted.

If it were me, double check the timing. Make sure the plugs and wires are in good shape. Can of carb clean and spray it down while running. Put in half a gallon of E85 in the tank. And take it for an hour long drive before rolling into testing. Get it fully warmed up, oil and everything, not just water temp.

The fully warmed up is often overlooked. Several short drives, idling in the driveway. The rich startup mix will get into the oil. As the oil warms up it dumps that fuel. PCV burns it through the engine. If the oil is warming up as you go to test, it is dumping fuel vapors into the engine. Fully warmed up, all the fuel is cooked out of the oil

 

[brbuilder]

Thanks for the responses.

I’ll replace the plugs, check timing, check PCV, change the oil and spray the carb with carb cleaner.

Timing chain and balancer have been replaced within the last year or so. Running a duraspark distributor, GM 4 pin module and motorcraft TFI coil. Also have a 195 t-stat installed and looks to be running about that temp on the gauge. Will confirm with infrared temp gun.

I’ve installed a charcoal canister that’s run to the bottom of the open element air cleaner. Wondering if disconnecting that for the emissions test would help. They don’t check under the hood for my ‘69.

Thought I had these emissions issues behind me after installing the q-jet. It’s been running good. Just don’t drive it enough. May have to look into the collector plates if I can’t get this figured out.

Thanks again for the help.

 

[brbuilder]

Replaced plugs with new Autolite AP45’s gapped at 44, replaced Pcv valve, replaced air filter, changed oil (Rotella 15w40), new Wix oil filter, set timing to 6 btdc, turned idle mixture screws in 1 turn, set idle to 1000rpm. I was down to 1/4 tank so I added 5gal of Sunoco 100 race gas. Thought that might help. Disconnected the hose from the charcoal canister to the air filter. Water temp showing 210 on the dash gage for test. Was typically 195-200. (Due to race gas? 6* timing?)

HC improved
HC loaded 302/was 320/450 std - PASS
HC idle 297/was 371/450 std - PASS
CO % got worse
CO loaded 8.93/was 8.77/3.75 std - FAIL
CO idle 8.19/was 5.55/5.00 std -FAIL

Guess I went the wrong way with my adjustments. Thinking I should adjust timing back to 12-16* btdc, adjust idle mix screws for max vac, readjust idle, then turn the idle mix screws in to get a 50rpm drop on idle. Am I heading in the right direction?

 

[Broncobowsher]

The race gas richened up the fuel mixture which brought up the CO. If you had done a gallon of E85, that would have leaned it out.

CO is a rich fuel mix that is burning. There is not enough oxygen.
HC is from a lack of fire. Too lean will make high HC. Partial misfires where parts of the mix don't burn. So hydrocarbons just bass out the exhaust. Bad ignition also increases HC. The fact you have decent HC numbers shows you have a pretty decent ignition system. You can get HC from a REALLY rich fuel mix. Where there is so much fuel that not only is the carbon not reducing to CO2 and making CO, but not even enough oxygen to make CO, so raw fuel just goes out the tail pipe. To get that rich, the CO will be as high as the meter can read.

Everything I see with your numbers is you are not burning oil and have a good ignition. You just have a rich fuel mix. Without actually tuning the carb, it can be leaned out by running oxygenated (alcohol enriched) fuels. Since the fuel brings some of its own oxygen, it needs less air to achieve the right mix.

 

[brbuilder]

I was debating on E85 or race gas. I guess I’ll run through this fuel and then put in a gallon of E85 and 5 gallons of reg unleaded. Hopefully that works. Also spray more carb cleaner.

Unfortunately it will be about a week before I can mess with it again.

Thanks for the help.

 

[toddz69]

The race gas richened up the fuel mixture which brought up the CO. If you had done a gallon of E85, that would have leaned it out.

CO is a rich fuel mix that is burning. There is not enough oxygen.
HC is from a lack of fire. Too lean will make high HC. Partial misfires where parts of the mix don't burn. So hydrocarbons just bass out the exhaust. Bad ignition also increases HC. The fact you have decent HC numbers shows you have a pretty decent ignition system. You can get HC from a REALLY rich fuel mix. Where there is so much fuel that not only is the carbon not reducing to CO2 and making CO, but not even enough oxygen to make CO, so raw fuel just goes out the tail pipe. To get that rich, the CO will be as high as the meter can read.

Everything I see with your numbers is you are not burning oil and have a good ignition. You just have a rich fuel mix. Without actually tuning the carb, it can be leaned out by running oxygenated (alcohol enriched) fuels. Since the fuel brings some of its own oxygen, it needs less air to achieve the right mix.

Would the old trick of adding rubbing alcohol (the 99% pure variety) help? That was one thing I did back in the day to help my carb'd truck pass.

Todd Z.

 

[Slowleak]

My Yukon used to fail. Emission inspector guy told me to dump Seafoam in the tank and come back. A bottle of Seafoam and a 15 mile drive got it to pass every year.

 

[Broncobowsher]

Would the old trick of adding rubbing alcohol (the 99% pure variety) help? That was one thing I did back in the day to help my carb'd truck pass.

Todd Z.

Exact same thing. Except E85 is bought at the pump for way less money. You are not buying a metal can, minimal retail markup, it is motor vehicle fuel.
Correct, same old trick from 30 years ago. If the CO is a little high across the board, lean it out with a fuel that has it's own oxygen on its back.

 

[DirtDonk]

set timing to 6 btdc, turned idle mixture screws in 1 turn, set idle to 1000rpm.

Don’t know about anybody else, but that seems like a lot. I would’ve just gotten it till it idled the best I could, and that would seem to be the most efficient way.
Do you know whether turning them in leans the idle mixture or richens it? I thought some carburetors were different than others, and I don’t remember how ours were.
At 1000 RPM, it might still be on the idle circuits completely, or it might be coming off of them too.
Might try all the suggestions the others have made, and then putting your idle adjustment back to normal.

 

[brbuilder]

PASSED EMISSIONS

Found a problem with the carb. Pulled the top off the Q-jet to check float level and discovered one of the arms on the primary power piston assembly that the metering rods hang from was bent up. Quite some time ago the carb was flooding/fuel pouring into the primary bores. I took the top off to check the needle and seat and found some debris, looked like flakes of solder in the bowl. I guess when I put it back together I didn’t get the metering rods and power piston assembly installed correctly and bent the arm. Luckily the metering rods did not get bent. Fixed that issue, set the timing to 16*BTDC, adjusted mix screws for max vacuum - 18.5 in hg, set idle speed to 700.

There was a long line so I sat and idled for probably 20min. I was getting nervous. Coolant temp was creeping up just over 190. Driving it stays just under 190. Guess advancing the timing to 16*BTDC helped reduce the coolant temp?

LOADED HC 222 (450 std)
LOADED CO 1.98 (3.74 std)
IDLE HC 447 (450 std)
IDLE CO 2.68 (5.00 std)

Guess I still need to figure out how to get that IDLE HC number down. Still had the Sunoco 100 race gas in it. Maybe that affected the IDLE HC reading.

Thanks for all the advice and to Broncobowsher for explaining what affects the HC and CO readings.

 

[Broncobowsher]

The 16° of base timing is giving you the high idle HC.

 

[brbuilder]

What do you recommend setting the timing at?

 

[Broncobowsher]

I would call for factory spec. If too far from factory, about 10°.
As the timing retards, manifold vacuum drops. This fills the cylinder with more air and fuel. The at idle cylinder pressure goes up. You get a cleaner burn. That is shown with the loaded HC being lower. The down side it without advance at idle the engine is very doggy. Part of the emissions era of engines having low power. Back in the day you would go to the local shop, they would tune to pass smog, and on the way back from the smog test you go back in and they would tune back to where it ran good. If it is running good now, just leave it.

It took me many years to learn the AZ emissions. If this, here are a few causes. I even managed to get a fully built stroked 5.0 engine installed in a Ranger to pass very clean. A copy of the emission test was part of what made the sale when sold.
When you are hosed is when the HC goes high because the engine is burning oil, or more correctly stated, passing unburned oil out the exhaust.

In your case the emissions test did exactly what it should do. Failed because you had an issue. You fixed. Now you are driving around with a cleaner vehicle. If you had not been tested, you would never have found the issue, and you would have been making a little more pollution. One vehicle is irrelevant, but collectively it adds up.

But you have passed. Good for another year.