What are your smog test results and what do they mean?

tbonertboner Member Posts: 402
edited March 2014 in Buick
I just had the Buick done on Thursday and of course it passed.

I wanted to compare the results with some others to see how clean the car is, and of course get some interpretation for these results.

I have the two tests for my Buick with me, and later I'll post the tests for the SVT done last year.

The test is the same done in many places, the IM240. In all cases, my car has fast passed. The Buick passed in 31 seconds this time, and in 110 seconds in 2001.

The standard allowed are:

For the 31 second fast pass:


There is no standard for CO2 or NOx

The 87 LeSabre with 126,6xx miles passed with


Two years ago, the car passed the IM240 in 110 seconds, so there are different standards for that test and the standards are:

CO=1.113 (says it is the 2nd Phase Fast Pass)

And my cars results with 73,xxx miles


I was hoping someone familiar with working with a 5 gas analyzer would tell me how my car might be doing and is it running clean enough to pass the emissions standards for a more modern car?

I'll post the Contour SVT results sometime as well for comparison.

The other thing is why such a great swing in the CO2 numbers? I'd expect the CO2 for the 110 second test to be greater than that of the 31 second test. I just wonder if these are peak levels or cumulative values. I've searched for details on the IM240 test, but haven't really found anything that helps.

Finally, the next smog for the SVT will simply be an OBD-II connection. If there are no codes and the MIL works, then the car will pass.

Why run cats at all if they are going to do that?



  • tbonertboner Member Posts: 402
    I kinda knew that stuff, I just wanted to see how my car compares, are the results good or bad for a 1987 and how it might compare to more modern cars.

    OBTW, the figures given in my results appear to be grams, not a parts per million value.


  • 0patience0patience Member Posts: 1,712
    I wish I could be more help, but since that isn't an area I deal alot in, that was pretty much the best I could offer. Maybe Alcan can give you some info on it.

    I wouldn't want to post something and be an alarmist. LOL!
  • andre1969andre1969 Member Posts: 25,606
    Just for a comparison, here's the results for my '00 Intrepid, when it went through last year:

    HC: 0.0070 GPM
    CO: 0.0002 GPM
    NOx: 0.0051 GPM
    CO2: 33.7203 GPM

    Just for kicks, here's my grandma's old '85 LeSabre, which was tested about 2 years ago:

    HC: 0.1622 GPM
    CO: 1.7541 GPM
    NOx: 0.2485 GPM
    CO2: 46.4807 GPM

    I don't know how things are in your area, but here in MD, your car would pass by model year 2000 standards, which are:

    HC: 0.7000 GPM
    CO: 15.0000 GPM
    NOX: 1.8000 GPM

    There is no standard for CO2, which is just a normal by-product of combustion. On the old tailpipe test (1984 and earlier cars here in MD), the CO2 test is actually a minimum, and not a max! Basically, if you're putting out a lot of CO2, that's a sign of a properly-running engine.

    As for why your CO2 went from 3.006 to 90.5, well both numbers sound whacked to me...unless your test is somehow different from the one here in MD. On my certificate, it just says "IM" for test type.

    Anyway, if they are similar tests, I'd expect your LeSabre to put out a bit more CO2 than my 2.7 Intrepid, but it shouldn't be putting out more than Grandma's old 307! Usually CO2 goes up with displacement. The automakers can try phasing out the other pollutants as much as they want, but as long as engines require oxygen and gasoline to burn, there's going to be a by-product of CO2, and bigger engines are going to suck down more air and fuel.

    I had heard somewhere awhile back that cars run so clean nowadays that it's almost impossible anymore to commit suicide from carbon monoxide poisoning. Judging from the results my Intrepid put out, I guess if I ever get the urge, I'll have to find another way to go!

    But then when I see that cars like Grandma's old '85 and your '87 LeSabre still pass by 2000 standards, in Maryland, at least, well that tells me that maybe older cars aren't so dirty, after all! Either that or the standards are too lax!
  • tbonertboner Member Posts: 402
    The IM240 test is an Federal EPA designed test on a dyno, that was meant to run for 240 seconds.

    Some enterprising folks figured out how to extrapolate results at set points in time to allow for a "Fast Pass" which is what my car has done on both occassions.

    I did a google search on IM240 and came up with a bunch of links, but most are either about the mathmatics behind fast pass or the repair actions. Well there were a few press releases that were long on praising the test and short on hard core technical details.

    Thanks for the datapoints.

  • andre1969andre1969 Member Posts: 25,606
    ...the link Opatience gave looks like it is for the old-style tailpipe test, where they do measure parts-per-million for HC and percentages for CO and CO2. Maryland doesn't test for NOX on tailpipe tests, for some reason.

    When I had my '79 NYer tested about a year ago, it scored:

    HC: 261 ppm (400 state standard)
    CO: 1.73% (4.00% state standard)
    CO2: 12.76% (6.0% state standard)
This discussion has been closed.