What causes high Carbon Monoxide (CO) emissions?

Great68 · Sep 8, 2004

Where I live they have this program called AirCare, it's an emissions testing program.

The retarded thing about this program is that even old cars like mine, or even older than mine have to be tested as well. (Cars that have no emission controls from the factory).

The test does an Idle test and a driving test of 40km/h. It tests your Hydrocarbons, Carbon Monoxides (CO) and Oxides of Nitrogen (NOx) emissions.

Now, I few past with flying colours for Hydrocarbons and Oxides of Nitrogen, but my CO emissions for the idle test were a bit above the limit, and my CO emissions for the driving test were almost twice the limit.

What could cause this, and how would I fix it?

Ozsum2 · Sep 8, 2004

It's your tune and/or the design. You need EFI and a cat to get the number THEY want.

John Z · Sep 8, 2004

Carbon monoxide results from incomplete combustion of fuel and is emitted directly from vehicle tailpipes. Incomplete combustion is most likely to occur at low air-to-fuel ratios in the engine. These conditions are common during vehicle starting when air supply is restricted ("choked"), when cars are not tuned properly, and at altitude, where "thin" air effectively reduces the amount of oxygen available for combustion (except in cars that are designed or adjusted to compensate for altitude).
http://www.nutramed.com/environment/carsepa.htm

Ozsum2 · Sep 8, 2004

Well, since you are at sea level, no air problem, and since the tests are done at operating temp, not choke problem either. There is no way our engines are going to pass a modern test without the mods I mentioned earlier.

Great68 · Sep 8, 2004

I did manage to get my car to pass last year, which was before the heads/intake/carb/cam swap.

Albeit just barely, my problem before was with high hydrocarbons at idle but I managed to lean it out enough that it would squeak through (I had a more radical cam before than I have now too). I never had a problem with CO.

BC_Ace · Sep 8, 2004

Aircare tests your vehicle to the specs of the date of manufacture, so updating to fuel injection or adding emmisions equipment isn't neccesary. Performance modifications do increase your emmisions output though. I've heard of guys having a spare carb with smaller jets that they use just to go through aircare.

Whenever I go through aircare, I've always had to detune my car by adjusting the timing and idle mixture, effectively making it run like ****. It won't pass if I leave it properly tuned.

I have a friend with access to a tune up machine with an exhaust sniffer I can play around with. Makes it a lot easier to see what your adjustments are doing.

Great68 · Sep 8, 2004

BC_Ace said:
I have a friend with access to a tune up machine with an exhaust sniffer I can play around with. Makes it a lot easier to see what your adjustments are doing.

Hook a brother up!!

Hack · Sep 8, 2004

Great68 said:
Where I live they have this program called AirCare, it's an emissions testing program.

The retarded thing about this program is that even old cars like mine, or even older than mine have to be tested as well. (Cars that have no emission controls from the factory).

The test does an Idle test and a driving test of 40km/h. It tests your Hydrocarbons, Carbon Monoxides (CO) and Oxides of Nitrogen (NOx) emissions.

Now, I few past with flying colours for Hydrocarbons and Oxides of Nitrogen, but my CO emissions for the idle test were a bit above the limit, and my CO emissions for the driving test were almost twice the limit.

What could cause this, and how would I fix it?

What temperature is your thermostat?

oh, here's another possible answer. The thing is, it's hard to get a performance engine to run lean enough without a computer and O2 sensor.
http://ca.autos.yahoo.com/maintain/emission_control_answer2.html

Great68 · Sep 8, 2004

Hack said:
What temperature is your thermostat?

oh, here's another possible answer. The thing is, it's hard to get a performance engine to run lean enough without a computer and O2 sensor.
http://ca.autos.yahoo.com/maintain/emission_control_answer2.html

I have a 195 degree in there right now.

I'm gonna have to find someone with a sniffer (hopefully Ace can help me out) Otherwise I'm just guessing when I fiddle with the carb, and could be spending $23 to run the test again just to fail again.

BC_Ace · Sep 8, 2004

Sorry, didn't mean for that to sound like I was offering up the machine. I have a hard enough time getting my car into his shop. Just a suggestion on what to do...

On a side note, are you going to be at the cruise in again this year? I checked your car out last year, but you weren't around.

Great68 · Sep 8, 2004

BC_Ace said:
Sorry, didn't mean for that to sound like I was offering up the machine. I have a hard enough time getting my car into his shop. Just a suggestion on what to do...

On a side note, are you going to be at the cruise in again this year? I checked your car out last year, but you weren't around.

Only if it's not pissing rain this weekend

Hack · Sep 9, 2004

Great68 said:
I have a 195 degree in there right now.

Ok, well I don't think that's it. I've seen some people on here run 160 degree units, and I thought if your car was running cold that would make a difference.

Cal Cobra · Sep 9, 2004

Hi guys, I have been a smog mechanic in Ca. for 20 yrs. I can tell you that CO is directly related to a/f mixture. By you mentioning that the HC level is good I know the engine is running well....just a little rich. First you should check and or lower the float level and if that is fine then you will have to decrease the main jet size until you reach the correct cruising a/f ratio. Remember to readjust the idle a/f mixture after any major changes inside the carb. What was your CO during cruise and what is the test limit?

Great68 · Sep 9, 2004

Cal Cobra said:
Hi guys, I have been a smog mechanic in Ca. for 20 yrs. I can tell you that CO is directly related to a/f mixture. By you mentioning that the HC level is good I know the engine is running well....just a little rich. First you should check and or lower the float level and if that is fine then you will have to decrease the main jet size until you reach the correct cruising a/f ratio. Remember to readjust the idle a/f mixture after any major changes inside the carb. What was your CO during cruise and what is the test limit?

Hey Cal,

Here's my car's readings and how much I'm allowed:

Driving Test:
Hydrocarbons (ppm): 121.00 - Max Allowable: 309.00
CO (%): 3.93 - Max Allowable: 3.32
NOx (ppm): 121.00 Max Allowable: 3702

Idle Test:
Hydrocarbons (ppm): 222 - Max Allowable: 916
CO (%): 7.14 - Max Allowable: 4.44

I made a mistake in my first post, it was the driving test that just barely failed on CO and the idle test that was a bunch above the limit.

So I guess I need to jet down a size, and lean out the idle mixture quite a bit. Sucks because the car runs really well right now as it is. Oh well, that's the trick to aircare, you gotta get the car to run like crap to make it pass and then you tune it all back the way you want when you get home.

Cal Cobra · Sep 9, 2004

By looking at your #'s you may not need to rejet at all. Since your idle mixture is very rich it will affect your cruise #'s. Just lean out your idle mixture (turn the a/f screw in) until you lose about 50 rpm ( this is called a lean-drop) and retest. It should pass. By the way those are very forgiving limits set by your state. I could get a smallblock with a 292* duration cam to pass with those limits...ask me how I know!

Great68 · Sep 10, 2004

Cal Cobra said:
By looking at your #'s you may not need to rejet at all. Since your idle mixture is very rich it will affect your cruise #'s. Just lean out your idle mixture (turn the a/f screw in) until you lose about 50 rpm ( this is called a lean-drop) and retest. It should pass. By the way those are very forgiving limits set by your state. I could get a smallblock with a 292* duration cam to pass with those limits...ask me how I know!

Do you have to emissions test old cars in California?

Cal Cobra · Sep 10, 2004

Years ago , we had to. At the present time if it is 30 yrs old or older it is exempt from testing. The toughest part of smogging old cars is finding old emission parts to bring them back to stock. Passing the sniffer is a breeze. How long have they been emission testing in BC?

Great68 · Sep 10, 2004

Cal Cobra said:
Years ago , we had to. At the present time if it is 30 yrs old or older it is exempt from testing. The toughest part of smogging old cars is finding old emission parts to bring them back to stock. Passing the sniffer is a breeze. How long have they been emission testing in BC?

They started up AirCare in 1992.

What causes high Carbon Monoxide (CO) emissions?

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