Question about 2000 Mitsubishi Galant

2 Answers

Emissions failing due to high nox

Took my mitsubishi through CT emissions 4 times and failed everytime on nox only, my numbers dropped a little everytime with repairs until i put the new egr valve on then my numbers shot up higher then they were in the first place and now i'm not sure what to do. new plugs new wires distributor and cap and router tryed the gas additives air filter evap canister cant afford a new cat so any help would be greatly appreciated.

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  • 8 more comments 
  • kim51581 May 20, 2009

    yes I got it really hot before testing it up and down the highway for atleast 30-45 min and I cant get the test done because my car is a 1994 they only test 1996 and above :-(

  • kim51581 May 20, 2009

    how do i check the vacum system? and how do i tell if the oxygen sensor is working?

  • kim51581 May 20, 2009

    when you advance the distributor does it increase or decrease the idle rpm? my levels were HC 97 CO 0.42 NOx 1965 the car has about 190,000 miles but runs great has a small idling problem though, idles up and down only once in a while could never figure out that problem. I had some muffler tape put on about a year ago in i believe three different spots would this in anyway affect the nox test? or clog anything that would affect the test? also on my last test the rpm was 1694 on this test the rpm was 0. I'm not sure what that means?

  • kim51581 May 20, 2009

    Test One HC 103 CO 0.37 NOx 1891



    basic tune up plugs wires air filter distributer cap, router then took

    Test Two HC 91 CO 0.40 NOx 1876



    tried the gas additives heet fuel injector cleaning etc.. then took

    Test Three HC 96 CO 0.43 NOx 1761



    replaced egr valve then took

    Test Four HC 97 CO 0.42 NOx 1965

  • kim51581 May 20, 2009

    I put the egr valve on and put it through emission test the next day after only driving about 30-45 min someone told me i should have drove it longer because it has to clear the stuff out is this true? my old egr valve was stuck... and as far as the cat being bad is there anything i can do to get it to pass the test without replacing the cat? I really cannot afford to do this.

  • kim51581 May 20, 2009

    I didn't give you negative feedback or a "thanks for trying" so I hope that comment was not directed at me... Thank you for your answers I will try what you said and see what happens

  • kim51581 May 21, 2009

    Ok just wanted to make sure... I am going to try what you said I'm just not exactly sure how to do this lol my email is @yahoo.com if there is anyway you could explain further? ... also someone told me to put a couple gallons of cam2 and 93 and run it like that then try the test again will this make a difference on the test or damage my car in anyway?

  • kim51581 May 21, 2009

    this is a 1994 not a 2000 somehow my listing was posted wrong and has 190,000 miles but still runs great

  • Greg Margossian
    Greg Margossian May 11, 2010

    If you could get a dianostics test performed (most auto parts chains perform them free), an error code(s) would be helpful in diagnosing your problem. Post back with error codes for more help.

  • yadayada
    yadayada May 11, 2010

    Did you get the car really hot before u tested it?

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  • Master
  • 2,559 Answers

NOx emissions are the result of high combustion chamber temps pure and simple. NOx readings go up whenever there are hot spots that exceed about 2400 degrees. Things like lean mixtures contribute to high chamber temps, as does over-advanced ignition timing.Lean mixtures are usually caused by some failed components or by air (vacuum) leaks in the intake.
Poor fuel quality contributes to detonation, another cause of high chamber temps.

  1. Check to make sure the vacuum system is tight.
  2. Try a full tank of high octane fuel(run at least half a tank through before testing)
  3. Have the tester do the rolling tests with the trans locked in first gear.
  4. Make sure the oxygen sensors is working.
If you have done all of this and still fail, You will need a new catalyst

Posted on May 20, 2009

  • Randy Hough
    Randy Hough May 20, 2009

    If the cat is bad a new EGR would make the numbers go up since the computer is trying to readjust the fuel air mixture to compensate for the new EGR,while the cat is still creating to much back pressure.

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  • Master
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I would closely examine what you did when you changed the egr valve, you want to make sure you're going forward, not backward in this repair. Make sure you have all connections back in place, electrical and vacuum. There are a few basic things that cause high nox. Generally speaking; the heat of combustion, but more specifically; a lean mixture, over advanced timing, or excessive compression. The lean mixture can be caused by a contaminated airflow sensor, I believe your car has an odd style of afm called a karman vortex meter, they have known problems. I wouldn't recommend playing around with this thing just yet, but something to keep in mind in case you have no choice. Make sure the air intake hose is well connected and no splits. I suspect it's your problem because you said all the other gases passed, it would be helpful to know their values. A lean mixture prevents the cat from lighting up completely. The cat must be fed exhaust with a minimum of .45 % CO content. Good emission repair shops will drill a hole ahead of the cat to insert their gas analyser tip in there just to measure pre-cat CO so they don't end up replacing cats for no reason. A brand new cat will do nothing to reduce nox without at least .45% CO. Has anybody measured pre-cat CO?
High compresson can be caused by combustion chamber deposits. If you do a lot of around town driving, it's possible there are deposits that have built up enough to cause a problem. A combustion chamber cleaning process may be beneficial, how many miles on this car?
Ignition timing is the single biggest factor in nox production, you must check it now! If it is correct, then your problem will be a bad cat if you know for sure pre-cat CO is .5% during the drive cycle. That said, some people that have engines with distributors can very easily cheat their way through the test by dropping their ignition advance about 10 degrees. This has a drastic effect on the production of nox and enables the car to pass the test. Dropping the advance has the detrimental effect of reducing power and gas mileage so these people usually put the advance back where it was meant to be after they get through the test.

Posted on May 20, 2009

  • 2 more comments 
  • Dave  C
    Dave C May 20, 2009

    The oxygen sensor is working just fine, you wouldn't have come close to passing the other gases unless it was.

  • Dave  C
    Dave C May 20, 2009

    I don't know who gave me the "thanks for trying" or negative feedback, I have an idea, but quite obviously you were not qualified to judge whether my information was helpful or not. Didn't *********** ever tell you, "if you haven't got something nice to say, don't say it" ? Perhaps you misjudged what I said when I mentioned what some people do to cheat, I didn't recommend this, it's just a fact. All the diagnostic information that I provided is correct and will lead this person to finding the cause of their problem and a cure. Just because you didn't like the news, it was no reason to shoot the messenger.
    Have a great day moron.

  • Dave  C
    Dave C May 20, 2009

    The readings you have posted indicate that the catalytic converter is completely finished, no longer working at all. If you re-read my post carefully you will see what some people do in your situation.

  • Dave  C
    Dave C May 21, 2009

    Kim, sorry about that, I knew it wasn't you. What I mentioned will work if you want to go that route.

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