Question about 1999 Chevrolet Cavalier
A couple of things; you can't have any leaks in the exhaust system, in front of the cat, and you must have the correct mixture going into the engine. The cat must have at least .45% CO going into it in order to reduce NOx. Make sure you have the correct fuel pressure, good fuel filter, and the engine is not running too hot when you take the test. In fact you may want to try a cooler thermostat. The oxygen sensor is only a fuel trim device, the bulk of the systems fuel control is dictated by the MAF and MAP sensor if it has one. Bottom line; your engine is running too lean or there is air getting into the exhaust system before the cat. You may want to try another MAF sensor if you know the other factors are good. If you have access to a gas analyzer, drill a pre-cat hole and check pre-cat CO under load, at least .45% is critical.
Posted on Jul 20, 2010
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Posted on Jan 02, 2017
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