Re: 2000 hyundai elantra acceleration questions
Drew,
If the catalyst in your vehicle were ailing, it would most likely be setting a P0420 "Catalyst inefficiency Bank 1" code. Hyundai's are real good about running there non-continuous readiness monitors, so a bad converter would set that code fairly quickly. Converters also don't regularly plug up like the old days. If they do, its usually the result of a melt-down caused by misfiring cylinder(s). Misfiring cylinders would have quickly set the check engine light, and possibly made the check engine light flash if it was bad enough (flashing MIL means misfire I.E. your cat is being roasted).
If you are still worried about the health of your cat, the best way to check it is with a scan tool that supports live PID info. You would monitor bank 1 sensor 1 and bank 1 sensor 2 O2 sensors for inversions (voltage switching which mirrors each other) by graphing the voltage. Ideally you want bank 1 sensor 2 voltage to remain at a constant number (voltage should be as close to a flat line as possible when graphed) once the cat lights off. Checking the vehicles stored Mode 6 data for the catalyst monitor will tell you how good or bad the converter has tested during its readiness monitor test. The old heat gun test (measuring the rise in the catalyst shell temp VS exhaust piping temp) will tell you if the converter is working, but it won't tell you how well its working.
As a previous poster suggested, it may be worth your time to check the vehicle out for something dragging. An emergency brake cable or rear brake component that is stuck may be dragging the rear wheels. A front brake caliper that has seized will do the same. Is your vehicle a manual transmission? A slipping clutch can for obvious reasons cause a lack of acceleration. Whens the last time its had a tuneup? Restricted fuel and air filters will affect performance. If the air filter is particularly dirty, you may also find that the hot wires on the mass air flow meter (MAF) are covered in junk. Your vehicle utilizes the MAF as its main way of calculating fuel delivery per given load, so a not so clean one will mess with your vehicles fuel trims.
