[KeithO]

My wife's car (1995 BMW 525i) has been slowly losing power and having reduced fuel economy over the last 18 months. I rarely drive the car. 2 years ago, it got about 32mpg on highway trips. Yesterday, I drove it for about 150 miles and only got 25-26mph.

It is down on power and very occasionally smells like a morning-after Guiness-fart. I am 90% sure that the cat is shot. I priced OEM replacement cats and every source I checked was in the $485-$500 range (yikes!). There is also the obvious choice of getting a universal cat and making it fit...

How can I be absolutely sure that this cat is bad? I'd like to be completely sure before I commit the time and potential effort on this.

Thanks

[231go]

How does one know if a catalytic convertor is shot?

How about when you shake it and something is rattling around inside.
My truck's cat is doing just that ....

There are two styles of converters, the older bead style that has many many millions of little BB looking things in there that get really hot and start glowing, and there are the ones that are the long rods and actually look like honeycombes. Your truck probably has the BB style being that its older and I don't thing those pluged up as quickly as the honeycomb ones. The bead ones have a little plug on the bottom where you can replace the beads themselve and reuse the old housing, but its actually easier to just order a new one and slap it on. But regardless of which one you have, they are really tightly packed inside and should not rattle around at all when you shake them. Given the age of your truck, assuming that your talking about the F-somethin or other tow rig, i would either just get a new highflow one or replace it with a straight pipe and be done with it. The old style converters were pretty restricitve compared to the new ones.