2003 BMW M3 Can't pass smog check in California

2003 BMW M3
82,000 MILES • 6 CYL • 2WD • AUTOMATIC
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LEXESTY
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Hello,

My BMW M3 has high HC (hydrocarbons) at
15mph measured 98 and the Max is 51,
25mph measured 77 and the Max is 35. I have done the tune-ups and oil change. The CO% and NO(ppm) passed without any problems. How can I bring down the HC reading? Does that mean my cats are bad?

Thank You!!
Nov 22, 2009 at 1:44 AM
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RASMATAZ
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My BMW M3 has high HC (hydrocarbons)

Hydrocarbon failures mean unburned gasoline is passing through the engine and entering the exhaust. The three most common causes include ignition misfire, lean misfire and low compression (typically a burned exhaust valve). Ignition misfire can be caused by worn or fouled spark plugs, bad plug wires or a weak coil. Lean misfire results where there is too much air and not enough fuel, so check for vacuum leaks, dirty injectors or a fuel delivery problem. In addition to these, hydrocarbon failures can also be caused by oil burning due to worn valve guides, valve guide seals and/or rings.
Nov 22, 2009 at 2:28 AM
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LEXESTY
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So, my cats should be in a working condition, correct? Will the HC be reduced if the old cats are replaced?

Thanks Again!!
Nov 22, 2009 at 3:18 AM
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RASMATAZ
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Will the HC be reduced if the old cats are replaced?

That's the Cat's job is to lower the HC/CO
Nov 22, 2009 at 4:25 AM