A: This problem is so common. A catalytic converter fails and gets replaced. The problem is that no one is checking to see why the converter has failed. A converter can fail in any one of three ways: It can start to leak externally due to rot; it can become clogged; or it can stop doing its job of cleaning noxious exhaust gasses. There are legitimate reasons for all of the above to occur, but as I said, no one is doing the diagnostic work to find why the catalytic converter failed. Some of the reasons may include, but are not limited to, a leaking fuel injector; a faulty mass airflow sensor; a vacuum leak in the engine; an overheating engine; or even a faulty fuel pressure regulator. Do bear in mind that some vehicles do not do well with after-market catalytic converters, and a factory unit is the preferred way to go.
Car Care Tip: When going for a Massachusetts state inspection sticker, make sure all lights and mirrors are working. State rules say all that lights and mirrors that came with the vehicle when new have to be working in order to pass inspection.
Larry Rubenstein is a master technician who owns a North Shore service station. His column appears every Saturday. Write to Larry at The Salem News, c/o Auto Scanner, 32 Dunham Road, Beverly, MA 01915, or send an email to firstname.lastname@example.org.