how to tell bad cats?
- Thread starter BlackVert
- Start date
gcomfx.com
Founding Member
It'll definately hurt gas mileage and top end of each gear. But I'm not sure how you actually test them. 
gcomfx.com
Founding Member
95redSVT said:bad cats? they piss and **** on everything in the house, claw up the chai....oh those cats
Not sure...mine have never given me a problem. They work well as wheel chauks
Makes them easier to kick when they are bad too. 
95strokerPSU
Member
mackey said:
Exactly. You'll know if they're bad just from the lack of performance. My first Mustang was a 2000 V6 and the cats melted down. In trying to figure out what the problem was the car was put on a dyno and was only putting 90HP to the rear wheels. I had a check engine light too.
with any exhaust restriction one can set up a vac gauge. rev up to a given RPM (say 3K). hold it super steady and watch the gauge. if the vac begins to drop, that suggests an exhaust restriction. diagnose the system from there.
good luck.
good luck.
I had a clogged cat eons ago when I still had the stock H-pipe on the car. The car bucked like I was learning to drive a stick shift all over again. It did this while driving and it took about 2 minutes for the car to get up to 40 MPH (and no, I wasn't flooring it).
You'll know it if the converter is clogged. The car will be slower than a lawnmower.
Joe
You'll know it if the converter is clogged. The car will be slower than a lawnmower.
Joe
DFG 5OH
Active Member
94CobraPace
Founding Member
The muffler shop I went to check the before cat & after cat temp & said it was bad, the temp was the same in & out. And no don't try to check you pet cats temp front & back, not a good idea..
HoofnIt
Founding Member
If the temp is the same, incoming and exiting, then why would they be bad? I've heard that when the cats are clogged or bad the cats will get extremely hot. If you have a laser/digital thermometer you can point it on the cats and get a temp.
Black Sun 5.0
Founding Member
From what I know of cats, they should be hotter, so the laser pointer isn't really the best way to go. You can bring the car to a shop and have the back pressure tested.
mo_dingo
20+ Year Stangneter 
ProKiller said:
But if they are clogged, then you won't pass inspection. Just saying.
Time for an o/r midpipe.
Scott
1994Vib.RedGT
Member
I dont know what would be wrong with them for this, but i remember one time the cats went bad on my moms Buick, and there was that sulfur/rotten egg smell. It was god awful
some folks will drill a small hole just before the cat. if air is screaming out the hole, that can suggest a bad (plugged) cat. same idea but w/o the variable of the car running funky w/o its lambda hooked up.matthiasj said:
