If it is just loosing efficiency, you can look at pre and post cat oxygen sensor readings on a scan tool(graph is best). If they are mimicking each other after fully warm, then the catalyst is non-functional. Engine performance and cooling are not affected, othere than a possible check engine light, and on 99, I don't believe it is monitored. Now, if it is coming apart, then it is restricting exhaust flow. Poor air out, is poor air in. You would perform what is called an exhaust backpressure test. There is a gauge to test this, but if you are having poor performance and suspect this, disconnect the exhaust prior to the cat, or remove a pre-cat oxygen sensor. Run it and see if it's improved. On a gauge reading, I think that anything over three is confirmed restriction. Be careful, because the cat is not the only thing that can cause an exhaust restriction. And yes, performance is degraded, and I would say it would run hotter.
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Thursday, August 27th, 2009 AT 10:54 PM
