Emissions test failed. Questions.
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Elder User
Joined: Mar 2003
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From: Hendersonville, TN
Emissions test failed. Questions.
Just ran my '86 351 HO (carbed) through yesterday. This year I got it pretty clean on the HC numbers (175 out of allowable 220), but failed on the CO numbers. (3.71. Max allowable is 1.20) what causes CO numbers to be high? They were low last year.
Elder User
Joined: Jan 2004
Posts: 767
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From: Franklin, GA
My experiences are that general maintenance items like new; air filter, proper heat range and correctly gapped spark plugs, plug wires, distributor cap and rotor button will all contribute to reduced CO (and HC) figures resulting from emissions testing. That's when I do the annual tune up on the only vehicle I own that requires testing. Passes every time (knock on wood) with flying colors! Others may chime in with other suggestions.
Freshman User
Joined: Sep 2003
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High CO = unburned fuel. Your engine could be running rich, (too much fuel or not enough air), or it's not burning all of the fuel,(ignition weak/misfire).
Too much fuel could be float adjustment, improper jetting,etc.
Not enough air could be dirty air filter, choke adjustment.
Unburned fuel could be plug wires, plugs, timing, cap, rotor, etc.
Did the engine produce excess CO at idle or under load?
Too much fuel could be float adjustment, improper jetting,etc.
Not enough air could be dirty air filter, choke adjustment.
Unburned fuel could be plug wires, plugs, timing, cap, rotor, etc.
Did the engine produce excess CO at idle or under load?
Postmaster
Joined: Jun 2004
Posts: 2,665
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From: B/CS, Texas!!
High Carbon Monoxide levels:
- Rich Fuel Mixture
- Plugged PCV Valve or fuel in the crankcase ventilation system
- Dirty Air Filter
- Malfunctioning closed-loop fuel metering system
- Saturated fuel evaporation canister or malfunctioning vapor purge system
I dont know if all these apply to your carbed engine. You could maybe try leaning it out when you take it back.
- Rich Fuel Mixture
- Plugged PCV Valve or fuel in the crankcase ventilation system
- Dirty Air Filter
- Malfunctioning closed-loop fuel metering system
- Saturated fuel evaporation canister or malfunctioning vapor purge system
I dont know if all these apply to your carbed engine. You could maybe try leaning it out when you take it back.
Elder User
Joined: Dec 2002
Posts: 713
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From: Houston U.S.
The other responces people gave you are good answers! But first let me tell you a little rule of thumb a harley davidson and auto mechanic told me once, and me trying it as well as others i have told, have found it effective in getting cars to pass emissions test. Fill your tank with high octane fuel, Texac always seemed the best to me on their super unleaded, then drive it at 70 for 30 miles, then when you get to the inspection station, DON'T KILL THE ENGINE! Let it run, until they get readdy for the testing for your sticker, it aids in burning off rich fuel and makes faulty emissions parts work better when they are hot. And of course change that darned oil, and put new plugs in it. This sounds stupid, but i have had many people praise me for telling them this little smart trick.
Janet
Janet
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Elder User
Joined: Mar 2003
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From: Hendersonville, TN
Thanks for all the replies. It's got fresh plugs, wires, cap & rotor, air filter and oil change. I failed to mention that the AIR pump isn't working. Maybe I under-estimated it's importance? Could it be that it's keeping the cat from burning off the excess fuel?
I always thought that it affected mostly the HC numbers.
I always thought that it affected mostly the HC numbers.
Elder User
Joined: Dec 2002
Posts: 713
Likes: 1
From: Houston U.S.
Yes, it could be leaving a little unburned fuel in your polution tubes, but if you run the thing for 30 miles and get it hot, it should suffice and pass, but you can go get a polution pump at a salvage yard for about nothing.
Janet
Janet
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