so after getting the "catalyst below efficiancy threshold" code about 5- 6 times, i guess its time for a new catalytic converter. i have a few questions about how my old cat may affect the performance of the car.

lately i've been thinking my tans was going bad, because the car has NO git-up-and-go when trying to merge with traffic or drive up a long, but not very steep uphill grade. does anyone else think that, if the cat is indeed plugged up, a new one would help remidy this situation?

also, i've been thinking about a new cat. probibly not a stock replacement ( friggin expensive) but more than likely an aftermarket one from jegs. however, before i spend ANY money, i wanna try "hollowing out" the cat already on the car. im not worried about emissions, im more worried that it will throw some kind of code from the downstreem O2 sensor and make the car throw more codes / run like crap anyway. would that happen with the OBDII system?

BTW the car is a '97 LS, all stock 3.1, original exaust as far as i can tell, and the car has 160,000 miles on it.

any help is greatly appreciated!

 

Yes your "trans" problem is probably the cat. Also if you hollow out your cat, you will still have the P0420 code.

 

Take it out. Best way to not have a cat clog up again

 

Keep in mind, some of the cheap aftermarket / "high flow" cats may still throw the engine code.

Have you tried going to an exhaust shop an seeing how much they want for an OEM replacement cat?

 

you could always run it without the cat or get an aftermarket cat and delete the code or buy an 02 emulator

 

Do you have emmisions tests around where you live? Why not get a straight through downpipe?? Then you could just find sombody that'll tune your PCM to turn the code off??

 

nope, no emissions around here, thank the lord, haha.

i'll probibly hollow it out or put a new section of pipe in, i just wanted to see if it would throw that code again.

if it still throws that code, will it throw the car into "limp home mode" trying to compensate for the emissions? like it did when my upstreem O2 sensor was bad? thats mostly what im worried about.

otherwise i think i know someone who can "fix" my pcm and ditch the code.

thanks for the great info guys!

 

The o2 sensor closest to the engine is the one you have to worry about. When I got my downpipe I was riding around with the check engine light on for a couple weeks and there was no problem cause it was the 2nd o2 sensor that was throwing the code.
Ive heard (make sure about this before you do it) that you can smack the cat with a hammer a bunch of times and it will loosen all that stuff up so you can just shake it out. I dont know if this is the best route to use but I have heard some people do this. But if you do, youre still left with the u-bend, or do you not have the ubend in the 5th gen??

 

i think the 5th gen cars dont have the u bend, not sure though. i think blacksheep mike is the one who mentioned it?

and actuallly the best way to hollow a cat out that i've found is using a steel bar to pound everything out of it. i've done a few, lol. but never done one on a car new enough to have the OBDII computer system and wanted to make sure it wouldint mess anything up. and now im fairly sure it wont thanks again guys.

 

You did read that it WILL throw a check engine light if you do that unless you buy an O2 sim for the rear O2 sensor or have the codes deleted in the pcm right?