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1999 Mitsubishi Eclipse Question: Spark Plug Gapping Creating Unburned Fuel Fail Smog



SICNIC9, 2.0L 4 Cylinder, San Diego, CA, June 06, 2010, 02:01

Check engine light is on, OBDII scan not helpful at all, fails emissions when ran at 2500 rpms 200 HC's where max allowed in CA is 130. Was told might be impropper plug gapping but we use pregapped plugs. O2 sensor is fine, found could be Exhaust Gas Recirculation Valve Replacement needed but info there says would fail for high NOx, we fail on HC's ...what else could it be?

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  • Answer #1

    September 19, 2014, 02:27

    "Cold spark". Hydrocarbons (unburned fuel) may be caused for several reasons:

    1) Leaking fuel injector causing rich combustion.
    2) you're burning oil. Check valve stem seals. At the 15 mph test, i failed at first because oil was seeping into the combustion chamber when the pistons are moving slower which causes cold spark, and to top it off, you can smell the fumes. At the 25 mph test, l passed with flying colors and the smell of unburned fuel disappeared.
    3) replace your coil pack too; that helped me pass!

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