The Stovebolt Site Forums The Shop Area Engine Shop On a Mission to Fix an Emission Condition

So I failed AirCare, our airquality testing.

Here's my results: 7.68% Carbon Monoxide when it should be no more than 4.49% on Driving test.

5.8% Carbon Monoxide when it should be 4.80 on Idle Test.

Any thoughts on the cheapest way to fix this? Is it timing?

Might help to know what type vehicle it is.

If you haven't already. Throw a full tune-up on the engine. When changing the plugs do 2 things -- read them for a rich or lean condition and make necessay adjustments to the fuel delivery system -- second run a compression and leak down test check on each cylinder.

I'm assuming that since you are posting on this site your vehicle is non-computer. However, it may still have an air pump and PCV valve -- check those for proper operation

I know people that have taken their catalytic converters off and still passed emissions by leaning their carbs out to where the engine will barely run. A slight advance in timing will also help. Once you have passed the smog test, reverse all of the adjustments that you have made.

twe56, I'm gonna try and figure out what you said and go through the manual. It's the original 235 engine in my 58. Air-pump - not sure if it does but don't believe so. From the sounds of it, it might be better for me to take it into the shop with their testing tools to do the adjustments.

SO, apparently old cars and trucks are not "grandfathered" (exempt) from emissions regs? That surprises me a little. If I remember my chemistry CO is a by-product of incomplete combustion. Improve the combustion and lower the CO. Have you had the truck very long? Has it been tested before? If so, I guess this is the first time it was over limit? I would say a fresh tune-up with a hot plug, the timing advanced as much as possible and still not ping, and as lean a carburetor mix as possible. Sorry, I don't have to worry about that in down-state Illinois. Let us know what works. If anyone thinks I'm wrong please correct. me.

I never heard of testing a 58. They didn,t come with any pollution devises. California had some retrofit at one time. Like the guys posted a good tune up might do it. You are not to far off. There used to be an additive for the gas that would make them comply but they may have outlawed it like they did the test tube. I would try to find some of that first.

magnolia,
You may want to change the oil then make sure you have the motor good and hot before taking it in (a few highway miles).
I had a suburban that failed and thats all it needed to pass, for a couple subsequent years, until I sold it.
Dan

Man, that is bad, emission tests for a 58?? I know that some provinces in Canada are a little different but that is really sad. People complain a lot in Ontario about having to test their cars up to 25 years old but we are lucky, I guess.

What is the hc of those readings. Here in BC even my 52 has to be tested.

You have emission tests on a vintage vehicle

Oh boy! Not even here in totaly over regulated Germany they send pre 1978 cars to that test.

Here is a trick we used with good results: Drive the tank almost empty and than buy a view gallons of the highest octan fuel in you can find.

Than enrich this with octan booster.
Now you can advance the ignition much more than usual.

Now create a temporal vacuum leak.

I don`t talk about pulling the wiper hose, but just let a bit air in the intake by loosing a clamp or something like this.

So you can lean it out better as with the air screw without hurting driveability to much.

It works like those air bleed gadgeds.

That should do the trick.

If you passed the test, go back to what you had.

good luck, Frank

High CO is an indicator of a rich condition. Start with the basics, like when was the last time the carb was rebuilt? Is the float level correct? Has it been modified? Rejetted richer for power? Issues or wear in the power valve circuit? CO numbers that high indicate you are dumping a lot of fuel.
Ignition timing will have little to no impact on CO. If HC's are high, retard the timing to decrease, right around TDC usually produces the best numbers, advancing the timing will make the HC numbers worse. If you have access to a gas analyzer, your CO and O2 numbers will cross or be equal when the air fuel ratio is correct.

John

There is a bunch of misinformation on this thread. Not trying to offend anyone on here but it seems like the only real help and understanding of high CO is john1. You are running too rich. Timing will not help this, oil changes will not help this, etc.. You need to adjust A/F ratio to correct this. Don't make vacuum leaks to compensate for it.

convert it over to propane may be cheaper in the long run and it will burn clean glad we dont have testing here