i have been told there is no real way to test them, but a crude test is to measure the tempature of the pipe just before the cat and just after, the pipe just after the cat should be hotter if the cat is doing it's job. at 170,000 miles the cat could easily not be functioning well anymore.
what kind of vehicle is it on?
[ January 14, 2004, 03:27 PM: Message edited by: tom slick ]