Passed smog; lessons learned

[CampoCougar]

Passing California's tough smog test is not always easy for our older Cadillac's. My '95 Seville failed three times, but passed today.   On previous attempts I had done all the normal prep. New filters, new o2 sensors, plugs and wires. Seam Foamed the intake, and ran two tanks of Techron, which smoothed out the idle. It came close on the previous attempt, only failing the HC @25mph by only 6 points a few months ago. Everything else passed at each previous test. The difference today was I finally threw in the towel and replaced the cat two days ago with a CARB approved unit, $300 installed, which was not too bad. This was on the advice of the state referee. He could see the car had no mechanical problem and ran smooth, and everything I had done. His quote:  "even though the NOX is low, a cat can get "weak and lazy" and not afterburn as well, resulting in high HC, even with lower than normal NOX. With everything I did, including the cat, I had about $450 into it, and well worth it. He was correct. The muffler shop said it was probably 10-12 years old and slightly heavy, indicating it was partially clogged. It passed, and the car runs better and cleaner. 

[Bruce Nunnally]

Surprising the cat still passed the car's checks but good fix.    Sounds like a good deal on the catalytic converter R&R.  I note that emissions gear normally has an extended warranty, so if you had been within 10 years that would have been something to consider.