High HC emissions (automotive)

Discussion in 'Mechanic and Repair' started by dfor, Mar 22, 2002.

  1. dfor

    dfor LawnSite Senior Member
    Messages: 829

    I don't remember if this forum is ok for auto questions, but I'll try. I have a 97 Honda Civic that went in for inspection. Didn't pass due to the HC emissions being too high. I replaced the distributor cap and rotor (after getting it back). Had already done the plugs & wires. Tomorrow I'm going to add a fuel system cleaner. Any help is appreciated. Thanks.
  2. khouse

    khouse LawnSite Bronze Member
    Messages: 1,465

    the rotor and cap really won't do it unless the engine had a miss in it due to the spark running down the inside of the cap to ground. I don't think the engine has a miss in it? make sure the timing is right on. I would still say it's an electronic component like O2 sensor or MAP sensor. You should have a trained mechanic run it through the computor to see what's really wrong.
  3. thelawnguy

    thelawnguy LawnSite Silver Member
    Messages: 2,411

    Have you changed the air filter? High HC generally a result of airway obstruction, misfire, car not warmed up to normal temp when tested, on a 97 Civic with EFI there would be a code set in the ECM if anything but plugged air filter.

    ERIC ROBERGE LawnSite Member
    Messages: 59

    What were the CO,CO+CO2, O2 and NOx readings? All of these readings need to be taken into consideration when diagnosing an emission failure by the gases. Was it a dyno test or a high and low idle test?
    I would agree with the Lawnguy. On anything 96 or later any component that would cause an emissions failure will more than likely turn on the check engine light. You probably need some routine maintainance or make sure the vehicle is properly warmed up. This includes the catalyst.
  5. dfor

    dfor LawnSite Senior Member
    Messages: 829

    HC GPM = 2.18 Limit of 1.84
    CO GPM = 13.34 Limit of 16.50
    NOX GPM= .91 Limit of 2.42
    CO2 GPM= 398.39 limit not specified

    I think it was on a dyno test. And by the way, the car has 184,000 miles (almost all highway). Check engine light not on. It does seem to be running a little better after the new cap and rotor. They only give you one free retry, then they hit you for another $47. Thats why I want to do what I can before I bring it back in.

    ERIC ROBERGE LawnSite Member
    Messages: 59

    I am not familiar with GPM. Here in atlanta ours are listed as percent or PPM.
    It looks like the CO is on the high side of the allowable range. I think. Like I said I am not familiar with GPM. I am assuming that is grains per million.
    How many miles on your catalytic converter? O2 sensor? Even though the check engine light is supposed to come on if they fail the components (and others) can be marginal but not bad enough for the PCM to recognize them as bad. A combination of "marginal components" can lead to emission readings just over the acceptable limit. That is not uncommon in high mileage cars.
    I am not familiar with Hondas specifically so I cant really give you any specific advice. If an oil change and tune up and some regular preventitive maintainance doesnt take care of the problem you will have to take it to a shop to have it diagnosed professionally. They should have the proper scan tools and can look into the PCM and deterimine what the sensors are reading and what the PCM is doing (fuel trim) and determine what could be the problem. The vehicles that fail by a little can be the hardest ones to diagnose. Make sure you go to a REPUTABLE honda specialist that can verify the repair does actually bring your emissions into acceptable limits.
    By the way,what is your fuel mileage? You may want to check it before and after the repair just for your own knowledge.

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