Cat converter Question

97 wrangler 4 cyl auto. I am told my coverter is after market and way over sized and was installed shotty....it rattled so we took it they stoped the rattle but its back again one day when i was a city away..a new rattle possible the clay inside...but as soon as this rattle began the engine seemed to loose power and the transmison stoped shifting right..eventualy it started to work right but I still toook it in anyways they said it was fine and it might be the engine or the converter thats causing the problem. So can my converter really cause this much havick?

Thanks Derek

I have a 95 that I had the worst problem with that. The converter element guts (if you've never seen one) looks like a honeycomb. It's ceramic, so it's brittle. Mine rattled loose and turned sideways, causing HUGE lack of power, because essentially you're choking off the exhaust. I can't say I saw tranny specific probs, but mine is manual.

Cheap solution - disconnect the cat, bash out the insides with a broom handle, and enjoy more power and better gas mileage.. but you didn't hear that from me.

i had the same problem with my 94 4.0L... one day i got a huge loss of power outta nowhere... i got to work and revved it up pretty high until the converter shot out the tailpipe like bullets... just dont stand behind it! i had to replace it afterwards for emissions laws and stuff up here but if you dont have to worry about those then you should be able to leave it.

I was thinking about doing a 3" pipe for my exhaust. Do the 4L need backpressure to run properly? I was thinking about doing it from the cat to the tail end.

Its not a good idea to run different size pipes on a car or anything. If there is 1.5-2" pipe coming into the exhaust then that is what you should run out of it. But hey that is my personal opinion. Although i think the 3 inch is a little over kill with the back pressure. maybe 2 inch or at most 2.5.

I will see what magna flow has, 2 or 2.5 is nice. I will do custom work, dual pipes looks best. Blended into my rear bumper.

I have to agree with stang, and I only speak from my limited exhaust experience. I had a weld go loose on some "custom" (hillbilly) work I did on my wrangler between the cat and the muffler, and the thing backfired like crazy. And, we're only talking like a decent little crack here, not total separation. I wouldn't go bigger ever, or you risk the same. Unless, you really want to go bigger, then create the backpressure with a more restrictive muffler, then bigger again after the muffler, but then what's the point.

Its for the looks!

You can go bigger with exhaust as long as you match the muffler for the correct back pressure and yes even a 4 liter needs back pressure or you will burn up the valves.