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Honda Civic DX fuel mixture too lean. What could cause this?

I took my 1992 Honda Civic to pass the smog check and they said the fuel mixture was too lean. I took my car to have the Catalytic Converter (CAT) tested and the said it wasn't that. What could it be?
Answer:

The smog check station which said the CAT is not the problem is correct. The Catalytic Converter has no control on fuel delivery or air/fuel mixture. A lean mixture could be caused due many things. You want to focus on possible vacuum leaks, defective oxygen sensor, defective fuel injectors, and/or defective ECT (Engine Coolant Temperature) sensor. Your best bet is to have a smog check repair station conduct a smog check failure diagnosis. They typically charge two hours of labor to do this. It will cost you a little bit (an hour of labor usually costs $50-$60), but it will help you avoid replacing emission parts which don't need replacing. posted by SmogTips Support

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