1992 Toyota MR2 SMOG TEST

1992 TOYOTA MR2
12,600 MILES • 4 CYL • 2WD • AUTOMATIC
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HERMIERLOPEZ
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  • 1 POST
iI brought my 1992 mr2 to smog station, it fails on HC which is over 100 points above
allowable, Pass the CO and NOX. what is the possible cause of this High HC?
Apr 14, 2009 at 10:34 PM
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RASMATAZ
  • ✓ASE Certified Mechanic
  • 75,992 POSTS
  • ASE Certified Mechanic
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.
Apr 14, 2009 at 10:46 PM
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