failed smog - high HC's - help please
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Pro
Joined: Nov 2002
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From: vista CA
failed smog - high HC's - help please
Got my 79 running and took it in for my first try at CA smog test yesterday(last tested and passed 3 years ago, I just bought it last month - did exhaust manifold replacement, front brake restore, front suspension restore, power steering restore to get it so I can at least drive it down the road safely). I failed the smog test miserably (hydrocardons really high at idle)!
My local smog test station was great about it - no charge, they said only the HC were way high at idle - they said it was running lean - and at higher rpm ran fine (HC in spec). Also notice a rough idle. So I am looking at vacumn leaks, idle adjust screws, etc. Tonight I noticed that my EGR valve won't hold a vacumn.
Should I just plug the vac line to EGR and go from there? Or is a functional EGR important to pass smog? Any good suggestions for what to look for? I plan on trying to adjust the idle mixture screws for best vacumn at idle, but figure the vacumn leaks/EGR ought to be fixed before trying that. Will also be looking to the lines and integrity of the vapor can.
....
:confused:
My local smog test station was great about it - no charge, they said only the HC were way high at idle - they said it was running lean - and at higher rpm ran fine (HC in spec). Also notice a rough idle. So I am looking at vacumn leaks, idle adjust screws, etc. Tonight I noticed that my EGR valve won't hold a vacumn.
Should I just plug the vac line to EGR and go from there? Or is a functional EGR important to pass smog? Any good suggestions for what to look for? I plan on trying to adjust the idle mixture screws for best vacumn at idle, but figure the vacumn leaks/EGR ought to be fixed before trying that. Will also be looking to the lines and integrity of the vapor can.
....
:confused:
Race Director
Joined: Sep 1999
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From: Plano TX
Re: failed smog - high HC's - help please (martinsw)
High HC is usually misfire. Vacuum leaks can cause misfires as can ignition related problems. Check vacuum leaks, plugs, wires etc.
Make sure the EGR works properly or you will fail NOx.
Make sure the EGR works properly or you will fail NOx.
Team Owner
Joined: May 2001
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From: Exiled to Richmond, VA - Finally sold my house in Murfreesboro, TN ?? Corner of "Bumf*&k and 'You've got a purdy mouth'."
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St. Jude Donor '06-'10, '13
Re: failed smog - high HC's - help please (zwede)
I would hook up a vacuum gage and then check each vacuum line branching from the carb. You can crimp the lines closed with a pair of pliers and watch the vacuum gage for a rise.
if the egr does not hold vac. that will be a problem. you can't just unhook it or you may fail if they do a visual inspection (they do that here in AZ). also another couple places to look would be the gasket under the carb, and the throttle shaft bushings. I would bet the bushings leak heavily. i think you can spray around them with starting fluid and if the idle changes it shows that the bushings are leaking and sucking in the fluid.
After you are sure you have no vacuum leaks, you can adjust the idle mixture using the vac. gage. You want to screw them both in all the way. Then bring them both back out 3 turns. start the engine and then turn each screw out equal turns on both sides. the vacuum should come up and at some point go back down when it gets too rich. From there screw them back in to get the highest vacuum reading, then screw them in one more 1/2 turn each. that will get you the best shot at idle mixture.
Also check and set your timing and idle speed. After jacking with the mixture screws the idle will be out of wack.
good luck !
if the egr does not hold vac. that will be a problem. you can't just unhook it or you may fail if they do a visual inspection (they do that here in AZ). also another couple places to look would be the gasket under the carb, and the throttle shaft bushings. I would bet the bushings leak heavily. i think you can spray around them with starting fluid and if the idle changes it shows that the bushings are leaking and sucking in the fluid.
After you are sure you have no vacuum leaks, you can adjust the idle mixture using the vac. gage. You want to screw them both in all the way. Then bring them both back out 3 turns. start the engine and then turn each screw out equal turns on both sides. the vacuum should come up and at some point go back down when it gets too rich. From there screw them back in to get the highest vacuum reading, then screw them in one more 1/2 turn each. that will get you the best shot at idle mixture.
Also check and set your timing and idle speed. After jacking with the mixture screws the idle will be out of wack.
good luck !
Le Mans Master
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From: Semper ubi, sub ubi
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Re: failed smog - high HC's - help please (martinsw)
The best advice I can give you is make sure that everything is in good tune, make sure your plugs and wires are in good shape, and you have a fresh oil change. Don't plug your EGR vacuum line, find any vacuum leaks and make sure your car is up to temperature before testing. Other things to try:
1. Retard your timing your normal timing should be 12 degrees btdc, try rolling it back to 6 or 8 degrees, this won't improve performance but it'll help with HC emissions.
2. Lean out the carburetor, do that with the idle air mixture screws on the front of the carb, do this after you've retarded the timing and with the car warmed up. Turn the idle mixture screws until the idling speed reaches its maximum. The adjust the idle speed screw until the engine is running at its specified idle, adjust in the mixture screws until the idle falls slightly(about 20-30 rpms) and the idle speed is rolling slightly. Then adjust the the idle mixture screws out about 1/4 turn. This ought to get you at the best lean idle condition.
3. Raise your idle to the maximum allowed by the Ca. laws for your car.
Good Luck!
:thumbs:
1. Retard your timing your normal timing should be 12 degrees btdc, try rolling it back to 6 or 8 degrees, this won't improve performance but it'll help with HC emissions.
2. Lean out the carburetor, do that with the idle air mixture screws on the front of the carb, do this after you've retarded the timing and with the car warmed up. Turn the idle mixture screws until the idling speed reaches its maximum. The adjust the idle speed screw until the engine is running at its specified idle, adjust in the mixture screws until the idle falls slightly(about 20-30 rpms) and the idle speed is rolling slightly. Then adjust the the idle mixture screws out about 1/4 turn. This ought to get you at the best lean idle condition.
3. Raise your idle to the maximum allowed by the Ca. laws for your car.
Good Luck!
:thumbs:
Le Mans Master
Joined: Oct 2002
Posts: 7,098
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From: Las Vegas - Just stop perpetuating myths please.
Re: failed smog - high HC's - help please (Smokehouse69)
Smokehouse gave good advice here as I remember high HC to be rich mixture. But I don't think you can adjust your initial timing here in CA as the machine verifies this at required rpm. Also the later Q-jets had the idle mixture screws slots capped to prevent tamper. But the smog station my not notice this if defeated.
I would verify the AIR pump and system is operating. You mentioned replacing an exhaust manifold? How about the little AIR tubes into the exh manifold? Did someone verify on replacement?
Get the engine warmed up with a little freeway use before testing.
How about alcohol blended fuel? May want to give it a try but suspect alcohol reduces CO or NOx more than HC.
I would verify the AIR pump and system is operating. You mentioned replacing an exhaust manifold? How about the little AIR tubes into the exh manifold? Did someone verify on replacement?
Get the engine warmed up with a little freeway use before testing.
How about alcohol blended fuel? May want to give it a try but suspect alcohol reduces CO or NOx more than HC.
Melting Slicks
Joined: Dec 2001
Posts: 2,321
Likes: 0
From: Reno NV
St. Jude Donor '08
Re: failed smog - high HC's - help please (cardo0)
I had the same problem on my 80......... Tried everything they mentioned already and it didn't help. I welded in a modern high flow cat and it breezed smog.
G/L I know how frustrating it can be.........
David
G/L I know how frustrating it can be.........
David
Thread Starter
Pro
Joined: Nov 2002
Posts: 599
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From: vista CA
Re: failed smog - high HC's - help please (martinsw)
Thanks for all the good advice everyone - this is a big reason I love this forum. I will replace the EGR & PVC valves (EGR needs it, pvc is just to cheap not to), brittle vac lines, oil & filt change, new plug wires, check valve lash&adjust if needed, check/set timing, and set the two idle adjust screws for max vacumn. Then maybe I will do better at a retest scheduled for later next week.
I did check for the air injection tubes when swapped out one exhaust manifold - one was missing (might have been why the driver side exhaust manifold burned out - coupled with lean running) - replaced w/new tubes.
If this doesn't do it, might be time to let the shop fiddle with it while hooked up to the sniffer (my appointment allows for this-extra time- if don't pass next time). Don't think I need a new cat - but could always be wrong...
I'll let you know....
I did check for the air injection tubes when swapped out one exhaust manifold - one was missing (might have been why the driver side exhaust manifold burned out - coupled with lean running) - replaced w/new tubes.
If this doesn't do it, might be time to let the shop fiddle with it while hooked up to the sniffer (my appointment allows for this-extra time- if don't pass next time). Don't think I need a new cat - but could always be wrong...
I'll let you know....
Melting Slicks
Joined: Dec 2001
Posts: 2,321
Likes: 0
From: Reno NV
St. Jude Donor '08
Re: failed smog - high HC's - help please (martinsw)
I didn't think I needed one either.......was just a temp fix. Got the cat really cheap. (can get another one really cheap too if ya have a welder and feel like cutting up your exhaust)
In any case. Good luck! And if ya get frustrated, just walk away!
In any case. Good luck! And if ya get frustrated, just walk away!
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Instructor
Joined: Jun 2000
Posts: 176
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From: Bakersfield CA.
Re: failed smog - high HC's - help please (88'Cubka)
Let me know if yr interested in a complete new exhaust system?, I just purchased a new SS complete system from mid america in Nov 03 (cause I thought Id have to wate anoughter year for my 75. no smog?), new from front y pipe,back through the mufflers and SS tips. only about 200 miles after install... Im going with side pipes ...Im in Bakersfield.CA.not sure if theres a difference between 75-79?, but I passed smog with them in Nov. on my L-48...
ps. I havent advertised them 4-sale, but wont need them much longer and thought ya might be interested?, (price ?, $300.00)
ps. I havent advertised them 4-sale, but wont need them much longer and thought ya might be interested?, (price ?, $300.00)
Race Director
Joined: Mar 1999
Posts: 10,258
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From: Calif.
Re: failed smog - high HC's - help please (martinsw)
http://www.recarbco.com/technical/index.html#smog
Excellent smog check troubleshooting guides here. Check it out.
Excellent smog check troubleshooting guides here. Check it out.
