1990 Caravan failed emission test NxO

Discussion in 'General Motoring' started by Awelch, May 18, 2005.

  1. Awelch

    Awelch Guest

    My 1990 Caravan work van failed one aspect of the emission control test.
    Hydrocarbons and CO tests were very good but NitrousOxide failed.
    Causes, they suggest, might be lean fuel mix, EGR valve or catalytic
    converter. Engine control error codes show 12 23 and 42.
    How would you proceed?
    Awelch, May 18, 2005
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  2. Awelch

    Awelch Guest

    PS It's a 3.0 FI engine here.
    Awelch, May 18, 2005
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  3. 12: Start of codes
    23: Air charge temperature sender improper value
    42: ASD and/or fuel pump relay circuit (Z1) fault

    Your "very good" HC and CO combined with high NOx suggests you're running
    lean, which could indeed be caused by the two faults your computer is
    squawking about.
    Daniel J. Stern, May 18, 2005
  4. Awelch

    vp17 Guest

    Just took my ’88 Caravan for the emission test and it failed as well
    for the same reason. HC and CO were fine but the NO was the reason for
    the fail (1156ppm limit was 979ppm). I’m gonna pull the codes (if
    there are any) later tonight. I might just fix the EGR and get it
    re-tested...don’t really want to change the CAT unless I really have
    vp17, May 19, 2005
  5. Awelch

    vp17 Guest

    Had no error codes on the caravan. I’m just going to test and change
    the EGR if it isn’t working properly according to the Haynes manual.
    vp17, May 20, 2005
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