Cannot pass emissions
Thread Starter
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Tuned
Joined: Apr 2023
Posts: 468
Likes: 67
From: Near SLC Utah
Cannot pass emissions
Hey all, I've been struggling to pass emissions these past 2 weeks. I passed the second time last year, I failed the first due to a bad plug wire, I thought I would pass this year but the truck had other plans. I am passing the hydrocarbons well, but I'm failing on the carbon monoxide. From the reading I have done, high CO is just incomplete combustion.
I pulled the plugs and they all looked healthy. I checked the fuel pressure and its 32 at idle and 40 with the FPR unplugged. The engine has a high compression ratio so I run 91 octane in it. I built a custom exhaust and put a high flow cat in it, it passed last year with this exhaust. I replaced the plug wires, cap, rotor, ICM, coil, and PIP recently. The air bypass and air diverter stuff and smog pump were not functional last year when I did the test and passed, so I removed them after the test. I pullled codes but just got 111 for koeo and then 412 for koer. The truck runs good, no major issues.
I am at a loss and I need some help, as always thank you guys so much.
I pulled the plugs and they all looked healthy. I checked the fuel pressure and its 32 at idle and 40 with the FPR unplugged. The engine has a high compression ratio so I run 91 octane in it. I built a custom exhaust and put a high flow cat in it, it passed last year with this exhaust. I replaced the plug wires, cap, rotor, ICM, coil, and PIP recently. The air bypass and air diverter stuff and smog pump were not functional last year when I did the test and passed, so I removed them after the test. I pullled codes but just got 111 for koeo and then 412 for koer. The truck runs good, no major issues.
I am at a loss and I need some help, as always thank you guys so much.
Mountain Pass
Joined: Mar 2008
Posts: 166
Likes: 38
From: SW GA
here is a link that may help. https://m.smogtips.com/failed-high-c...onoxide-CO.cfm
non-ethanol or with?
non-ethanol or with?
Thread Starter
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Tuned
Joined: Apr 2023
Posts: 468
Likes: 67
From: Near SLC Utah
Thank you for the link I have made a list of everything I am going to check. The list includes: TPS, MAP, ECT, HEGO, engine compression, oil contamination, PCV, fuel filter, air filter, injectors, computer/fuel trim, cat, ACT, fuel pumps, and FPR.
This was with ethanol, I decreased the octane rating of the fuel to 85, or thats what the pump said, since it passed last year on 85, but no avail. The previous tests were done on 91 octane, but they had almost the same exact results.
This was with ethanol, I decreased the octane rating of the fuel to 85, or thats what the pump said, since it passed last year on 85, but no avail. The previous tests were done on 91 octane, but they had almost the same exact results.
Cargo Master
Joined: Mar 2007
Posts: 2,825
Likes: 1,030
High HC is caused by incomplete burning. Basically, some of the gas does not get burned so the gas [HC] just goes out the tail pipe. Lean mixtures cause high HC, vacuum leaks seem to be the biggest reason.
High CO is usually the fuel mixture is too rich.
Basically, I would start knowing there were no air leaks. Have someone do a smoke test if you can't. All the air must be metered and if you got a leak, it just makes it harder to pass the emissions test. Fuel pressure is important. Injector balance is also important.
High CO is usually the fuel mixture is too rich.
Basically, I would start knowing there were no air leaks. Have someone do a smoke test if you can't. All the air must be metered and if you got a leak, it just makes it harder to pass the emissions test. Fuel pressure is important. Injector balance is also important.
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Lead Driver
Joined: Sep 2002
Posts: 9,540
Likes: 2,031
From: North Texas
Check the brake booster grommet. They die with age. Bypass anything else off the vac tree.
100% agree on injectors. They flow all over the place with age...these trucks are over 30 years old and need the injectors serviced.
Did I miss if V8 or L6?
100% agree on injectors. They flow all over the place with age...these trucks are over 30 years old and need the injectors serviced.
Did I miss if V8 or L6?
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Thread Starter
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Tuned
Joined: Apr 2023
Posts: 468
Likes: 67
From: Near SLC Utah
High HC is caused by incomplete burning. Basically, some of the gas does not get burned so the gas [HC] just goes out the tail pipe. Lean mixtures cause high HC, vacuum leaks seem to be the biggest reason.
High CO is usually the fuel mixture is too rich.
Basically, I would start knowing there were no air leaks. Have someone do a smoke test if you can't. All the air must be metered and if you got a leak, it just makes it harder to pass the emissions test. Fuel pressure is important. Injector balance is also important.
High CO is usually the fuel mixture is too rich.
Basically, I would start knowing there were no air leaks. Have someone do a smoke test if you can't. All the air must be metered and if you got a leak, it just makes it harder to pass the emissions test. Fuel pressure is important. Injector balance is also important.
Thread Starter
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Tuned
Joined: Apr 2023
Posts: 468
Likes: 67
From: Near SLC Utah
I will check all the vacuum lines. The injectors are not factory so they have been replaced, I recently took them all out and blew them out with carb clean to remove any trash inside them, but they were all clean. Its a 351w.
Thread Starter
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Tuned
Joined: Apr 2023
Posts: 468
Likes: 67
From: Near SLC Utah
I rebuilt the engine last year around this time, so the plugs have been in since last year along with a new set of wires. I did take out all the plugs and they all looked healthy, they were also gapped correctly. I recently changed the cap and rotor. I replaced the fuel filter in November of last year. I just did an oil change, and installed a new air filter, a couple of weeks ago.
Thread Starter
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Tuned
Joined: Apr 2023
Posts: 468
Likes: 67
From: Near SLC Utah
I was curious about the catalytic converter that I installed last year, mainly I was wondering if it was getting up to temperature to actually do its job. I can't really stick a thermometer in the cat so I measured the outside temp of the cat and it was 70* F after letting it idle for about 10 minutes. Took it for a drive on the interstate and then measured it and it was at 110*F. Outside temperature is around 40*F. I would think that it would be a lot hotter, the long tubes and y pipe were about 350*F but as soon as it hit the cat it drops significantly. This may be a big contributing factor, I will do some more research into the exterior temperature of catalytic converters but ideally I would like to measure the internal temps.
Lead Driver
Joined: May 2011
Posts: 5,776
Likes: 443
I was curious about the catalytic converter that I installed last year, mainly I was wondering if it was getting up to temperature to actually do its job. I can't really stick a thermometer in the cat so I measured the outside temp of the cat and it was 70* F after letting it idle for about 10 minutes. Took it for a drive on the interstate and then measured it and it was at 110*F. Outside temperature is around 40*F. I would think that it would be a lot hotter, the long tubes and y pipe were about 350*F but as soon as it hit the cat it drops significantly. This may be a big contributing factor, I will do some more research into the exterior temperature of catalytic converters but ideally I would like to measure the internal temps.
Thread Starter
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Tuned
Joined: Apr 2023
Posts: 468
Likes: 67
From: Near SLC Utah
