How do you adjust carb...

[72gmcshorty]

I failed my emmisions testing. I had a high CO reading. How do you adjust the carb to lower this?

[whitesswj]

what kind of Carb do you have? that is the number one question. and two did you run some carb cleaner through the tank??


I just want to add that I love ARkansas. there's no safety or emmision testing. we dont' care if you run a POS or the like or if it runs bad either.

sswj

[72gmcshorty]

it's an edelbrock and no I didn't run anything through it.

[shifty]

I like Atlanta. No emissions on vehicles 20yrs old or older. I only pay $180 per year for indurance w/full coverage on my truck and a $250 deductible. Good deal.

Is there a FAQ article on carbs? Like, how to tell if you're burning rich or lean, how to adjust for diff't gas levels, etc?

[CHEVY & GMC FOREVER]

I don't think there's emissions testings on cars/trucks older than 30 years in Illinois either.

[72gmcshorty]

So can anyone help answer my question? I'm guessing those two dial like things in the front of the carb are part of the solution. About 2 years ago when I failed the first time, I had the smallest jets for this carb put in and it passed no problem. I didn't touch the carb after that. Since then the truck has been sitting and I just started driving it again. Siphoned out the old gas, put in new gas and drove. I didn't spray any carb cleaner though. Anything else I could do?

[curbyk]

Air filter clean?

[pjmoreland]

If you have the smallest jets, the carburetor could be running too lean, which will cause inefficient combustion. Take a look at Edelbrock's website for a wealth of information on tuning their carbs. Here's a chart they have on their website for selecting the right jets and metering rods. You might also have a problem with your ignition system. Replacing the cap, rotor, spark plugs and wires couldn't hurt.

[Jeremy_5]

Well first you need to know where your car is running lean vs. rich. CO comes from incomplete combustion so like someone else said it could also be ignition related. One cylinder could be misfiring, or something like that the problem may not be the carb.

Do you have the rest of the exhaust gas numbers? If you do use this chart and try to figure out if you are running rich... or if you have the numbers post them and I will try to figure it out

[cableguy0]

an engine that sits too long needs to be driven and kinda get all the crap cleaned out that builds up from sitting.

[greenhorn male]

Hi CO usually means you are running too rich. A dirty air filter or not enough Oxygen could cause this to happen or just too much fuel to air ratio. I don't know much about engine tuning or carburetor adjustment but I know little about emissions. The two screws you mentioned is the fuel mixture adjustment. Maybe someone will advise the proper way to adjust your mixture. A misfire will cause unburned gas (raw gas) to pass through your tailpipe, therefore you will get high HC's (hydrocarbons) and not high CO from a misfire. If you pull a plug wire your HC's will jump up and not CO. If you lean out your carburetor too much you will get a condition called lean idle missfire and produce high HC's also. A vacuum leak will produce the same result. Since your failure was CO then your problem should be carburetor related. Your not getting enough oxygen to combust the fuel completely. So either you have too much fuel or dirty jets. If I remember correctly dirty jets would produce an undesirable spray pattern and therefore not atomize the fuel for complete combustion. CO= imcomplete combustion, HC= unburned gas.
My guess would be to make sure the jets are clean, your air filter is clean and air cleaner is functioning and adjust the fuel mixture down but not too low that it starts missfiring.

[wxman1]

I seem to remember a device that you could screw into the plug hole.
It functioned as a spark plug but it would allow you to "see" the combustion.
Apparently, the color of the flame would tell you whether you were
running rich or lean. Never saw this device, but several board members
commented on it some time back. Don't know what its called. Anybody
have any more info?

Jim
Mt Juliet

[68speedalert]

I assume your truck had just an idle test, probably in park/neutral.

You might replace points and condensor and check timing, if you have points.

Everything others had said about filters and running rich are dead on. Try pulling the PCV out of the valve cover and listen to the engine. If the speed changes at all, change the oil, it could be saturated with gas.

To adjust the idle mixture, let truck idle until completely warm. Make sure the choke is wide open. If it isn't then that's your problem. If open, turn each mixture screw in a 1/4 turn at a time. Listen to the engine idle (preferably with a tach). Turn them the 1/4 turn until you hear it slow down. Then turn them out 1/8 to 1/4 to make it smooth out. Do it a couple of times to make sure. This should get you close.

BTW, 25 year old cars don't get sniffed in Missouri anymore.