lostbuckaroo

Well my 98' has been throwing the P0420 code for the past couple of weeks. I've already determined I'm going to get new O2 sensors, due to the high mileage (200K) and not really knowing the vehicle history other than how it's running now after pretty extensive maintenance, and the 703 injector swap. I've been looking online and and found a video by Walker Exhaust... I found that I'm temp testing the converter wrong. And will need to retest.

Here's the video:

I temped my exhaust system tonight after a trip to town and back with the engine and exhaust fully warmed up. I suspect the converter is indeed bad. Wanna do all the homework I can before I replace it.. The California models are EXPENSIVE!!

Down Pipe Temp - 497 Degrees (Taken where the pipe crosses over from the diver side)

Converter Temp - 389 Degrees (Taken in the middle of the converter on the bottom side heat sheild) wrong way to temp it according to the video

Muffler Temp - 297 Degrees (Taken in the middle of the muffler body)

rrich

Rev and hold it at 2000RPM for 2 minutes, let it idle.
Go under - measure at the inlet then at the outlet. If it's working right, it'll be about 100 degrees HOTTER at the outlet.

Get one from a small independent muffler shop - ask a smog station who it good and cheap - they'll know.
Chain stores, MIDAS etc are waaaay too high, dealers are even higher.

Internet you'll get the wrong one.

Bustedback

You're most likely going to need a new catalytic converter.

lostbuckaroo

Yeah it's been far more difficult than one would think finding the correct converter for California.

I emailed Magnaflow and they directed me to part #46736 after looking it up on Summit Racing's site under the description it states: "California Legal: No" ..

I emailed Walker Exhaust and they replied: "We appreciate your interest in our products. I am sorry but we do not offer any CARB certified converters for your 1998 Cherokee 4.0L."

Why is it so hard to get a straight answer!? Good suggestion though. I'll have to go to the local SMOG station and ask.

lostbuckaroo

Update: After email about the conflicting information on the the SummitRacing web site I heard from a rep at Magnaflow and he stated:

"This part has been approved for sale in California and has a California E.O. # on it. As long as the EFN on your vehicle’s emission sticker matches the # I circled in red the converter is legal for your vehicle in the state of California. I will contact summit and see if can make it more clear on their website EFN #WCRXT0150110"

Maybe this will help other "Do-It-Yourselfers" here in California. EDIT: I still need toe verify the EFN number on my XJ though.

Bustedback

I have never seen a smog tech check the numbers on a catalytic converter, they look to see if there is one and can tell if it is working, but never record the numbers. If the cat looks like it has been installed recently and looks like a DYI install, they may take a closer look though.

lostbuckaroo

I hear ya. My XJ was smogged in late October this year before I bought it so I shouldn't have to SMOG for a few years. However knowing my luck I better make sure everything is to the letter of the law otherwise they'll give me trouble. Also know that they are stricter in some counties than others. I happen to live in Sacramento County.. so.. it's pretty strict. Although I plan on doing it myself I'm replacing the muffler and tailpipe as well so it will be done right. I'm considering welding it all as well. No clamps.

rrich

As of about 2 or 3 years ago the law changed.
They have to have a CARB stamp on the bottom. Supposedly the smog tech is supposed to see it.

But they rarely look.

A small independent muffler shop in your area will have one in stock and will be the right one, and legal.

Why make it complicated trying to get one mail-order? In the end you'll screw yourself.

They'll have 2 sizes - a small one for rice burners, a larger one for big engines. The big one is very low restriction for our little 4.0's.

lostbuckaroo

Well I temp tested again this morning (the correct way). The inlet was 85 to 95 hotter than the outlet. That pretty much confirms it. Need a new one. I'm gonna go ahead and replace everything from the cat back. Whom ever had it before me did a system on it and tied into the original down pipe (or made a new one). Right under the bell housing the pipe goes into a small barrel I'm assuming at 2" then comes out 2.5"diameter... What is this? A resonator??? What's the pourpose? Also the down pipe has a big dent just below the flange where it connects to the manifold.. Is this stock?? I think I've read somewhere this is important to create back pressure at the manifold??

Here's a pic of the barrel thing I'm asking about..

Bustedback

The dent in the down tube is for front drive shaft clearence, I have no idea what the buldge is for, maybe your engine ate a rat.

lostbuckaroo

Any other opinions? The dent is way up on right next to the flange right where it connects to the exhaust manifold. Should I leave this barrel thing or re-do the downpipe all together?

Bustedback

Trust me, the dent on the down pipe is for drive shaft clearence when flexing.

lostbuckaroo

Trust ya man.. now what to do about this growth on the pipe... hmm... ??