[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

[Sam Strano]

The smell could be a bad cat. or could be shitty gasoline.

Other things that happen when cats fail: Mileage suffers, higher RPM performance sucks, since the exhaust is restricted. Car may run warmer than normal if it's REALLY bad.

BTW, I can get you a converter for less than the dealer. Direct fit, the whole deal. FWIW. And the tune-up parts, brakes, shocks.... you get the point. (IMG:http://www.frrax.com/rrforum/style_emoticons/default/wink.gif)

Pellet style converters haven't been used in about 20 years on anything. Everything uses a monolithic cat now. And they aren't bad in terms of flow or life. Often cars lose power without them. Hollowing one out isn't a good idea (though cheap). It screws the flow up terribly since you have a big 'ol empty room that the air wants to fill. That makes a LOT of turbulence, which isn't good. Besides, Keith lives in Pittsburgh, and they have smog testing there.