1995 Chevy Camaro California smog test

EDMAN

MEMBER
1995 CHEVROLET CAMARO
V8
2WD
AUTOMATIC
98,540 MILES

My 1995 Z28 has recent rebuilt heads, new plugs and ignition wires, a seven year old replacement cat converter, runs very good with no check engine light showing, but fails the smog test due to high HC reading at idle and cruise speed on the roller dyno. Can the oxygen sensors be the culprit even though the car has no trouble codes, or do you think the converter is more at fault?

Saturday, January 31st, 2009 AT 12:21 AM

1 Reply

RASMATAZ

MECHANIC
75,992 POSTS

HC 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

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Saturday, January 31st, 2009 AT 12:43 AM