failing Calif smog

[tim dobbins]

Hopefully someone can help. We have a 1996 993 with 45K miles that we can't get to pass HC for Cal smog. We have changed the following: new plugs, caps, rotors and spark plug wires. We have reset all 6 readyness codes twice and drove directly from there to the smog station without shutting down the engine which was about 30 miles. During pretest the system showed high HC. Max 54 @ 15 mph and measured 85. Max 37 @ 25 mph measured 61. CO was fine. On the readyness status sheet it showed only 3 monitors ready, misfire, fuel system and comprehensive components. All others read not ready.

Even though we clear all codes they seen to reset themselves so the car does not do the initial set up for smog. Has anyone had this problem and does any have a solution. Thanks

Tim

[Garageboy]

Tim,

If the HC (hydrocarbon) is high then one might theorize that the engine is not getting enough O2 (oxygen). In other words not enough air is in the charge as the injector supplies the fuel. Chemists call this stochiometric when the fuel is properly balanced with the O2 to give a complete burn of all the fuel.

Your Oxygen sensor may be lazy and slow providing the engine management processor with a signal that is causing the rich condition.