Failed Emission Test
Thread Starter
Pro
Joined: Nov 2001
Posts: 534
Likes: 6
From: Cave Creek AZ
Failed Emission Test
My 72 LT-1 recently failed the AZ emissions test. It passed under load and failed at idle. It has a new MSD ignition system that is set at 36 degrees total advance (before mech adv).
I am trying to fine tune the carb (original Holley, recently restored) to lean out the idle and balance that off with maintaining a reasonable idle speed and mixture. I am also not running the original AIR pump (not sure that makes a big difference).
I have read some of the tuning posts here. I have adjusted the mix screws on either side of the front of the carb - about (a little more than) one turn out from lightly seated. How should the accelerator pump be adjusted? I believe that if it is set to aggressively it could be adding fuel at idle... not sure how I would know if it is set properly.
Any other suggestions from the crowd?
Dave
I am trying to fine tune the carb (original Holley, recently restored) to lean out the idle and balance that off with maintaining a reasonable idle speed and mixture. I am also not running the original AIR pump (not sure that makes a big difference).
I have read some of the tuning posts here. I have adjusted the mix screws on either side of the front of the carb - about (a little more than) one turn out from lightly seated. How should the accelerator pump be adjusted? I believe that if it is set to aggressively it could be adding fuel at idle... not sure how I would know if it is set properly.
Any other suggestions from the crowd?
Dave
Race Director
Joined: Sep 2001
Posts: 10,560
Likes: 439
From: Wellington, FL
St. Jude Donor '11 thru '25
Yes it sounds like you are running a little rich. I had a problem with my '76 like that I pulled the air filter element and breezed right through. I don't believe there is an adjustment for the accelerator pump.
Race Director
Joined: Sep 1999
Posts: 11,360
Likes: 382
From: Plano TX
The accelerator pump does not add fuel at idle.
Look down the carb with the engine @ idle & air cleaner off. You should NOT see any fuel dripping from the boosters. If there is fuel dripping, post back and I can walk you through the common causes of this problem.
If there is no fuel dripping it is probably just the idle mixture screws. To pass you should turn them in until the idle rpm starts to drop.
Look down the carb with the engine @ idle & air cleaner off. You should NOT see any fuel dripping from the boosters. If there is fuel dripping, post back and I can walk you through the common causes of this problem.
If there is no fuel dripping it is probably just the idle mixture screws. To pass you should turn them in until the idle rpm starts to drop.
Instructor
Joined: Dec 2005
Posts: 190
Likes: 0
From: Hot AZ
If your not going to use it as a daily driver and can wait until 2qtr of 07 you can skip the tests altogether...
In 2005 the Arizona Legislature passed House Bill 2357, which amended the Arizona Revised Statutes (ARS) at § 49-542 to authorize the exemption of certain collectible vehicles and motorcycles from being subject to the emissions testing requirements.
ADEQ..."On Dec. 12, 2006, EPA signed a proposed approval of the exemptions . The proposed approval was published in the Federal Register on Dec. 28, 2006. Proposed EPA actions are also subject to public review and comment. EPA then responds to any comments received and publishes a final action. Final EPA action on the exemption request is expected by the second quarter of 2007."
http://www.azdeq.gov/environ/air/vei/motor.html#epa
In 2005 the Arizona Legislature passed House Bill 2357, which amended the Arizona Revised Statutes (ARS) at § 49-542 to authorize the exemption of certain collectible vehicles and motorcycles from being subject to the emissions testing requirements.
ADEQ..."On Dec. 12, 2006, EPA signed a proposed approval of the exemptions . The proposed approval was published in the Federal Register on Dec. 28, 2006. Proposed EPA actions are also subject to public review and comment. EPA then responds to any comments received and publishes a final action. Final EPA action on the exemption request is expected by the second quarter of 2007."
http://www.azdeq.gov/environ/air/vei/motor.html#epa
Thread Starter
Pro
Joined: Nov 2001
Posts: 534
Likes: 6
From: Cave Creek AZ
I found this as http://www.bob2000.com/carb.htm
"Accelerator Pump arm adjustment: The accelerator pump arm must not be loose at idle. The .015 clearance is measured at wide open throttle (engine off!). This is to prevent damage to the pump arm and diaphragm. You may need to adjust the external spring one way or the other to get it tight at idle, yet still have the .015 clearance at WOT."
So here is part of my answer.
My plates expire in Feb, I need a clean emission test to get a renewal. Doesn't the new AZ law also restrict mileage and require collector insurance? I am not cool with restrictions on how/when I can drive the car.
"Accelerator Pump arm adjustment: The accelerator pump arm must not be loose at idle. The .015 clearance is measured at wide open throttle (engine off!). This is to prevent damage to the pump arm and diaphragm. You may need to adjust the external spring one way or the other to get it tight at idle, yet still have the .015 clearance at WOT."
So here is part of my answer.
My plates expire in Feb, I need a clean emission test to get a renewal. Doesn't the new AZ law also restrict mileage and require collector insurance? I am not cool with restrictions on how/when I can drive the car.
Drifting
Joined: Sep 2004
Posts: 1,959
Likes: 1
From: North Bend Ohio
My 72 LT-1 recently failed the AZ emissions test. It passed under load and failed at idle. It has a new MSD ignition system that is set at 36 degrees total advance (before mech adv).
I am trying to fine tune the carb (original Holley, recently restored) to lean out the idle and balance that off with maintaining a reasonable idle speed and mixture. I am also not running the original AIR pump (not sure that makes a big difference).
I have read some of the tuning posts here. I have adjusted the mix screws on either side of the front of the carb - about (a little more than) one turn out from lightly seated. How should the accelerator pump be adjusted? I believe that if it is set to aggressively it could be adding fuel at idle... not sure how I would know if it is set properly.
Any other suggestions from the crowd?
Dave
I am trying to fine tune the carb (original Holley, recently restored) to lean out the idle and balance that off with maintaining a reasonable idle speed and mixture. I am also not running the original AIR pump (not sure that makes a big difference).
I have read some of the tuning posts here. I have adjusted the mix screws on either side of the front of the carb - about (a little more than) one turn out from lightly seated. How should the accelerator pump be adjusted? I believe that if it is set to aggressively it could be adding fuel at idle... not sure how I would know if it is set properly.
Any other suggestions from the crowd?
Dave
Now, get a vacuum gauge on this engine. Set the idle speed at about 800 RPM. Adjust the idle mixture screws until you have the highest idle speed. KEEP THEM EVEN! Now, back off each idle mixture screw until you see a 25 to 30 RPM decrease in engine idle speed for each screw. That's a total of 50 to 60 RPM. Reset the idle speed with the idle speed screw to whatever you want, say, 700 or 800 RPM.
Also, can you give us some numbers that you scored on the test?
BigBlockk
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Tech Contributor
Joined: Aug 1999
Posts: 14,373
Likes: 6,371
From: At my Bar drinking and wrenching in Lafayette Colorado
Lars
Le Mans Master
Joined: Jan 2000
Posts: 8,918
Likes: 27
From: New Hill NC
Whos standard? California or Federal? I am sure it had to pass the standard of the time, but probably not the modern standards. What does AZ use as a standard for that car today? We have never tested anything pre-cat. in NC, and now dont test anything but OBD2 which is 96 and newer, and that is not a sniff test. They just plug up to the data link and take the readings from it.
Thread Starter
Pro
Joined: Nov 2001
Posts: 534
Likes: 6
From: Cave Creek AZ
Failed at Idle, passed at Load
Idle:
HC standard: 400 ppm, my car: 491 ppm
CO standard: 5.00%, my car 7.85%
I believe these are AZ standards but not too sure.
I am running the original Holley 6239 carb, it was just restored by Chicago Corvette. Sorry but in the earlier post I meant 36 degrees before vacuum advance. I believe the initial is 12 degrees, gonna check it again this weekend. I am also cleaning up the smog pump and may put it back on...
Thanks for the help!
Idle:
HC standard: 400 ppm, my car: 491 ppm
CO standard: 5.00%, my car 7.85%
I believe these are AZ standards but not too sure.
I am running the original Holley 6239 carb, it was just restored by Chicago Corvette. Sorry but in the earlier post I meant 36 degrees before vacuum advance. I believe the initial is 12 degrees, gonna check it again this weekend. I am also cleaning up the smog pump and may put it back on...
Thanks for the help!
Last edited by DSchaefe; Jan 30, 2007 at 06:13 PM.
Race Director
Joined: Mar 2006
Posts: 14,112
Likes: 28
From: Florida
It seems that once all the junk was off the road, then they did away with the testing since most vehicles are now obdll and FI anyway.
Race Director
Joined: Sep 1999
Posts: 11,360
Likes: 382
From: Plano TX
BTW, when new these cars idled at 1-2% CO.
Melting Slicks
Joined: Aug 2006
Posts: 3,429
Likes: 20
From: Kingston Ontario
Priceless
What to do and what to adjust depends on what you failed: Did you fail on hydrocarbons or CO? If you failed HC, you can adjust the carb all you want, and it won't make you pass. Give me your reading numbers and I'll tell you how to set it up to get it to pass. Also let me know what type of carb you have along with the carb number (if you failed CO)
Lars
Lars
No testing for over 20yr cars here.
Racer
Joined: Dec 2006
Posts: 417
Likes: 40
From: Swansea IL
Emissions Levels
Zwede and Lars,
In the past when my car didn't pass the emissions tests here in Illinois, my mechanic buddies told me to always change the oil just befoe I took the car for testing. Evidently old oil contributes to one of the emission levels. Which one, do you know?
When I did this all my numbers where much lower than the standard. I also adjusted my idle mixtures screws as had been suggested and the 1970 454 passed with flying colors.
Bob
In the past when my car didn't pass the emissions tests here in Illinois, my mechanic buddies told me to always change the oil just befoe I took the car for testing. Evidently old oil contributes to one of the emission levels. Which one, do you know?
When I did this all my numbers where much lower than the standard. I also adjusted my idle mixtures screws as had been suggested and the 1970 454 passed with flying colors.
Bob
Team Owner
Joined: Jan 2007
Posts: 53,648
Likes: 878
From: Southern Cal Ca
St. Jude Donor '22
I am surprised the missing pump doesn't fail you.
Also stock timing.
Yes fresh oil, Drygas in the fuel, hotter thermostat
help.
The air pump does put clean air in the exhaust.
Proper idle adjust is done with tach and vacuum gage.
Adjust each air screw to max rpm and highest vacuum
then turn in untill 25 rpm a side 50 total drop.
Sometimes power valves leak if to close to idle vac.
Here in cal they would not even test if any part is not there
(air pump) let alone improper idle speed and base timing.
Also stock timing.
Yes fresh oil, Drygas in the fuel, hotter thermostat
help.
The air pump does put clean air in the exhaust.
Proper idle adjust is done with tach and vacuum gage.
Adjust each air screw to max rpm and highest vacuum
then turn in untill 25 rpm a side 50 total drop.
Sometimes power valves leak if to close to idle vac.
Here in cal they would not even test if any part is not there
(air pump) let alone improper idle speed and base timing.
Thread Starter
Pro
Joined: Nov 2001
Posts: 534
Likes: 6
From: Cave Creek AZ
Here in AZ they didn't even pop the hood to look at the engine bay. I am planning to get it warmed up and put the timing light and Vac gauge on it this weekend, and probably re-mount the AIR pump.
Last edited by DSchaefe; Jan 30, 2007 at 11:24 PM.