diagnosing bad cats

scottzg · Post by **scottzg** » Fri May 14, 2004 10:30 pm

So, back in the day i was told that my catalytic converter was failing. I did nothing about it. I dont trust the shop that gave me this tip. I'v watchd my mileage slowly drop lately. I suspect the cat, as otherwise the car is fine, maybe a tad sluggish. How do i diagnose it? we've got 3 cats, right? (i havent seen my car in 3 months) I only have a week at home to fix it, then im driving to idaho, so could i just hollow out the problem cat and save some time and money temporarily? This would help fwy mpg, no? Thanks a lot!

petridish38 · Post by **petridish38** » Fri May 14, 2004 11:34 pm

I'm not exactly sure how to diagnose the catalytic converters, but I watched the people at my muffler shop and they banged on them and told me they were bad.

You could just hollow it out as a new cat would run you anywhere from $700 and up (at least it was for my mom's protege).

We only have two cats.... one right under the passenger side inner CV joint and the other a little farther downstream. (non-turbo)

If the cats are the cause of the MPG, then hollowing it out would help.

Andrew

scottzg · Post by **scottzg** » Sun May 16, 2004 4:14 am

how does a good cat sound compared to a clogged one?

petridish38 · Post by **petridish38** » Sun May 16, 2004 7:57 am

That's what I don't know... I was under the car with him while he was looking at it for something else, and he banged the cats and said they were bad as well.

Don't know if they were just trying to screw with me or not, but they were probably telling the truth... I just don't know what its supposed to sound like...

But again....you could take a chance and hollow it out.If its bad its probably not doing anything just sitting in there, so u might as well take it out...

Andrew

vrg3 · Post by **vrg3** » Sun May 16, 2004 8:03 am

They might have banged them and heard stuff inside rattling around or something.

I know when I took the dead catalytic converter out of my brother's exhaust and turned it on its end, lots of debris poured out.

evolutionmovement · Post by **evolutionmovement** » Sun May 16, 2004 5:32 pm

Older cats had ceramic pellets in them which made them more restrictive and they get loose. I think the newer style is a less restrictive honeycomb or something, so I'm not sure if it would rattle with loose stuff. Either way I have the original cats on my car and passed MA emissions very easily. Here they put the car on a dyno to test it and run it through the gears and back down - not just a sniffer at idle. The exhaust on these cars, like practically everything else, seem to be pretty long-lived - unlike the older models. Mine's all original, but the muffler's finally starting to go.

Steve

Brat4by4 · Post by **Brat4by4** » Sun May 16, 2004 8:02 pm

Yes, rattling inside of the cat means it is way past due. Go ahead and gut it or put on a new one. I had a '84 Olds Delta 88 that had a clogged cat. It killed the performace like mad, once that bad boy was replaced it felt like a new engine.

If you're car is AWD... I have never heard of any country, county, munincipality, or province that has a 4WD dyno for emissions testing. That's when you get to do the "no load" testing. Stinking 1-wheel drivers think they know everything

evolutionmovement · Post by **evolutionmovement** » Sun May 16, 2004 10:10 pm

I was making a point that the cats can be pretty long lived, nothing about dyno-testing an AWD. I'm well aware they just get the idle sniffer here. I'm also trying to say that I'm not sure if we have a newer style of cat that may not rattle when hit even if it is bad - I know at some point they stopped using the highly-restrictive ceramic pellet design that rattled when bad.

Steve

aspect · Post by **aspect** » Sun May 16, 2004 11:25 pm

Cut off the cats and go full 2.5in straight through headerback. Better than spending money to fix parts you don't need or want. =D

scottzg · Post by **scottzg** » Mon May 17, 2004 2:44 am

aspect wrote:Cut off the cats and go full 2.5in straight through headerback. Better than spending money to fix parts you don't need or want. =D

that a lot of exhaust for a n/a. And as a californian, having a functional cat at smog test time is handy.

BAC5.2 · Post by **BAC5.2** » Mon May 17, 2004 5:36 am

Andrew - If you paid $700 for a new cat, you got SCREWED. Not just a little, but a LOT. You can get a new, high flow cat, for around $150.

Gut the cats and leave it at that.

How, exactly, do you gut the cats? And where are the cats in a turbo? Mid-pipe and where?

THAWA · Post by **THAWA** » Mon May 17, 2004 6:37 am

and downpipe

BAC5.2 · Post by **BAC5.2** » Mon May 17, 2004 7:09 am

Oh, that's right. It's the up-pipe that is catless in our cars. I thought it was the downpipe for some reason. Thanks!

petridish38 · Post by **petridish38** » Mon May 17, 2004 11:44 am

BAC5.2 wrote:Andrew - If you paid $700 for a new cat, you got SCREWED. Not just a little, but a LOT.

I'm not sure how much they are for our cars... I was going by how much one was for my mom's 1999 protege. Good thing it was covered under warranty. I'm pretty sure one of her's cost that much... but I could be wrong, but from what i've heard, they can be expensive.... I will look at the records later today and see.

Andrew

evolutionmovement · Post by **evolutionmovement** » Mon May 17, 2004 5:56 pm

I've never been sure of how effective performance cats are in terms of functionality from an emissions stand point, but real cats are expensive. They contain rhodium and platinum and neither metal is getting cheaper - in fact quite the opposite. Even old clogged cats are worth $30 bucks at a recyclers around here. No idea what they get out of them, but considering the cost of processing, they must make a fair amount of money on the final product. The demand for platinum is getting higher as more people seem to want it for jewelry and more labs use them for experiments. I believe fuel cells also use platinum, but I could be remembering that incorrectly.

Steve

madmonkey · Post by **madmonkey** » Sun May 30, 2004 12:22 am

[quote="BAC5.2"]Andrew - If you paid $700 for a new cat, you got SCREWED. Not just a little, but a LOT. You can get a new, high flow cat, for around $150.

Where exactly can I get a $150 cat? Which cat are we talking about?

legacycentral bbs

A forum for 89-94 BC-BF(BJ) Legacy Owners and Fans

diagnosing bad cats

diagnosing bad cats