Can't Pass Emissions
Post Fiend
Joined: Feb 2008
Posts: 5,831
Likes: 121
From: St Albert, Alberta
Replaced the brake booster and sealed up an open vacuum port. Started her and she sounded horrible. Was about die out. So the previous tune was setup for high idle mixture. Turned the idle mixture in till I hit the bottom then turned a 1/4 counter clockwise and now running great. Just fine tuned the carb after that. I made 3 full turns on the idle mixture screw till I hit the bottom so no wonder why my truck was guzzling gas before. This should help lower the CO output now correct? Since now I'm not flooding my engine with gas?
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New User
Joined: Nov 2016
Posts: 15
Likes: 0
From: Mesa, AZ
I was feeling frosty enough to take my truck back for emissions testing to see if I had improvements. Here were the readings and results...
Emissions Readings:
I think I got to replace my catalytic converter. I tested it with a temp gun I borrowed from my neighbor (who is awesome because he's got a chevelle). The temperature of the pipe in front of the cat converter was colder than the pipe exiting the cat converter. Cat converter obviously isn't doing it's job anymore. While I'm at it, I will probably replace the O2 sensor as well (located for me toward the bottom of the exhaust manifold, where the exhaust manifold meets the cat converter). I will also check my secondary air injection.
Emissions Readings:
Code:
Pollutant | Vehicle's Emissions | Standard Emissions | Result
--------------------------------------------------------------------
HC | 4.68 | 3.00 | FAIL
--------------------------------------------------------------------
CO | 143.48 | 25.00 | FAIL
--------------------------------------------------------------------
NOX | 0.95 | 4.50 | PASS
Post Fiend
Joined: Feb 2008
Posts: 5,831
Likes: 121
From: St Albert, Alberta
I was feeling frosty enough to take my truck back for emissions testing to see if I had improvements. Here were the readings and results...
Emissions Readings:
I think I got to replace my catalytic converter. I tested it with a temp gun I borrowed from my neighbor (who is awesome because he's got a chevelle). The temperature of the pipe in front of the cat converter was colder than the pipe exiting the cat converter. Cat converter obviously isn't doing it's job anymore. While I'm at it, I will probably replace the O2 sensor as well (located for me toward the bottom of the exhaust manifold, where the exhaust manifold meets the cat converter). I will also check my secondary air injection.
Emissions Readings:
Code:
Pollutant | Vehicle's Emissions | Standard Emissions | Result
--------------------------------------------------------------------
HC | 4.68 | 3.00 | FAIL
--------------------------------------------------------------------
CO | 143.48 | 25.00 | FAIL
--------------------------------------------------------------------
NOX | 0.95 | 4.50 | PASS
Your HC (Unburnt Hydrocarbon) is lower (almost there).
The secondary air system looks to be functioning (at least partially), but verify.
But CO (carbon monoxide) is way to high this is symptomatic of a cat this is not working properly or combustion issues (see below)
You will need to set the carb with a vacuum gauge. Your NOX is actually bit low indicating cold combustion this could be a function of timing , idle air not quite dialed in or leaking EGR valve or the system not working properly. Cold combustion can raise CO levels.
Double check your cat and post the temps with the engine at idle at operating temp. We will be bale to tell you is the cat is good or marginal.
FTE Legend
Joined: Nov 2015
Posts: 30,960
Likes: 4,129
From: Angier, NC
I would say wile in there checking things check the choke that it is opening all the way other wise it will run rich.
It seams a lot of our older trucks the part(s) that heat up to open the choke fail / rust.
Dave ----
It seams a lot of our older trucks the part(s) that heat up to open the choke fail / rust.
Dave ----
New User
Joined: Oct 2016
Posts: 15
Likes: 0
Im in the exact same situation than you! Same carburetor, does anyone knows how to tune them? I having a hard time finding infos online...
Just got back from the inspection and my result were:
HC: reading 1990. Limit 220 FAILED
CO: reading 12.05 Limit 1.2 FAILED
Co2: reading 6.2 Limit N/A PASS
Anybody knows what I should do? I just got back my truck after an engine swap and I think I need to tune the carb before going back, I was idling at around 950/1000rpm, maybe thats the explanation?
Just got back from the inspection and my result were:
HC: reading 1990. Limit 220 FAILED
CO: reading 12.05 Limit 1.2 FAILED
Co2: reading 6.2 Limit N/A PASS
Anybody knows what I should do? I just got back my truck after an engine swap and I think I need to tune the carb before going back, I was idling at around 950/1000rpm, maybe thats the explanation?
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New User
Joined: Nov 2016
Posts: 15
Likes: 0
From: Mesa, AZ
Back to working on my truck today. Finally gave in and had my emissions checked out by a mechanic. He looked at my catalytic converter and could tell already that my cat was burnt. They cut it off and we saw that the cat was burnt inside. Getting a new one welded on as I type. Now I know what a burnt cat converter looks like 
. I guess running the truck with the vacuum leak and idle mixture turned up to compensate for so long it burnt my cat converter.
. I guess running the truck with the vacuum leak and idle mixture turned up to compensate for so long it burnt my cat converter.
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Post Fiend
Joined: Feb 2008
Posts: 5,831
Likes: 121
From: St Albert, Alberta
Back to working on my truck today. Finally gave in and had my emissions checked out by a mechanic. He looked at my catalytic converter and could tell already that my cat was burnt. They cut it off and we saw that the cat was burnt inside. Getting a new one welded on as I type. Now I know what a burnt cat converter looks like . I guess running the truck with the vacuum leak and idle mixture turned up to compensate for so long it burnt my cat converter.
. I guess running the truck with the vacuum leak and idle mixture turned up to compensate for so long it burnt my cat converter.The cat would not melt at idle not enough heat or flow, that would happen at higher engine RPM's. Replacing the O2 sensor is the correct move you should always replace the O2 sensor when you do the cat/cats any way, just a good practice...
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New User
Joined: Nov 2016
Posts: 15
Likes: 0
From: Mesa, AZ
Be sure the AIR injection is working properly. It will generally take care of most (not all but most) of the extra hydrocarbons in the exhaust.
The cat would not melt at idle not enough heat or flow, that would happen at higher engine RPM's. Replacing the O2 sensor is the correct move you should always replace the O2 sensor when you do the cat/cats any way, just a good practice...
The cat would not melt at idle not enough heat or flow, that would happen at higher engine RPM's. Replacing the O2 sensor is the correct move you should always replace the O2 sensor when you do the cat/cats any way, just a good practice...
New User
Joined: Oct 2016
Posts: 15
Likes: 0
Back to working on my truck today. Finally gave in and had my emissions checked out by a mechanic. He looked at my catalytic converter and could tell already that my cat was burnt. They cut it off and we saw that the cat was burnt inside. Getting a new one welded on as I type. Now I know what a burnt cat converter looks like . I guess running the truck with the vacuum leak and idle mixture turned up to compensate for so long it burnt my cat converter.
. I guess running the truck with the vacuum leak and idle mixture turned up to compensate for so long it burnt my cat converter.Just by curiosity, how could they know that it was your cat converter? I wonder If I have to replace mine too but Id love to be sure before I actually do it. Also how much did it cost you? just to have an idea
Thanks!
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New User
Joined: Nov 2016
Posts: 15
Likes: 0
From: Mesa, AZ
We negotiated a price and was able to get $100 for part and labor. He welded it in in less than 10 min.
Post Fiend
Joined: Feb 2008
Posts: 5,831
Likes: 121
From: St Albert, Alberta
You need to test the pump to make sure the pump is pump actually moving air,
that the diverter valve/s are working, that the check valve is only flowing one way, that the piping is intact and not blocked and that the control system is working. With out seeing the emissions sticker I can not really give you a step by step.
Thread Starter
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New User
Joined: Nov 2016
Posts: 15
Likes: 0
From: Mesa, AZ
You need to test the pump to make sure the pump is pump actually moving air,
that the diverter valve/s are working, that the check valve is only flowing one way, that the piping is intact and not blocked and that the control system is working. With out seeing the emissions sticker I can not really give you a step by step.
that the diverter valve/s are working, that the check valve is only flowing one way, that the piping is intact and not blocked and that the control system is working. With out seeing the emissions sticker I can not really give you a step by step.