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Aug 4, 2021 | 10:39 PM

#16

doublechaz

Senior Member

Joined: Aug 2020

Posts: 614

Likes: 205

From: Prescott, AZ

Year: 1988

Model: Cherokee (XJ)

Engine: 4.0

I should mention that I did my replace because jumped timing led to my injectors firing twice for each cycle. It would barely run like that. I had 7 psi exhaust pressure they were so carboned up by the time I figured out what was going on. The internet cleaning methods did not work at all so I had to replace.

Aug 5, 2021 | 10:26 AM

#17

robsjeep

CF Veteran

Joined: Dec 2017

Posts: 1,529

Likes: 412

From: San Mateo, CA

Year: 1990

Model: Cherokee (XJ)

Engine: 4.0 Renix, stock.

Quote:

Originally Posted by doublechaz

You can always hollow out the old cat, and run with it, no ill effects on drivability. save the new cat for test time. wink wink.

Aug 5, 2021 | 11:44 AM

#18

Madcap

Thread Starter

Junior Member

Joined: Mar 2020

Posts: 57

Likes: 1

From: Oregon

Year: 1996

Model: Cherokee (XJ)

Quote:

Originally Posted by BlueRidgeMark

Well, you have a 96, so the only thing that code is doing is to tell you to fix your cat. The data from the rear O2 sensor is not used by the PCM for running the engines. (There's a sticky at the top of the forum about it. I hear the fella who wrote it up is kinda dumb,and really ugly, but despite that, he got it right by reading it straight out of the factory service manual.)

The later models did use the rear O2 sensor(s) to manage the fuel, so it's a bit more complicated. I'm not sure yet what year switched over, but I know my 97 wasn't using the rear for engine management. I suspect they switched when they went to the coil pack waste spark ignition.

Anyway, it's not a problem on your 96.

As to making the CEL go out, well, I like your thinking. Makes life a little tougher than the "I don't care" crowd, but I like it. Maybe there is an electronic method to fool the PCM. Find out what a good cat looks like to the PCM, and mimic it.

I did a quick search and found a few options:

http://www.colorado4x4.org/vbb/showt...-sensor-bypass

https://duckduckgo.com/?t=ffsb&q=mim...=v171-1&ia=web

Thanks for all the input everybody. @BlueRidgeMark , I appreciate all the info, especially the referral to that sticky by that ugly dumb bastard.

My first step is going to be to try the spark plug non-fouler and see if I get lucky. If the Jeep stops spending my money the way it has been to bring it back to health, I'll look at the CATs in another year. The USPS maintenance allowance only goes so far, and I've done a tranny rebuild AND engine replacement in the last 12 months.....so yeah.

Thanks again people! I will update with my results when I get to it.....might not be until September.

Aug 5, 2021 | 12:17 PM

#19

Saudade

CF Veteran

Joined: Aug 2020

Posts: 2,152

Likes: 585

From: SoCal

Year: 1988

Model: Cherokee (XJ)

Engine: 4.0L

Well, not to be "that guy" but here goes. It's a violation of Federal law to tamper with the emissions system on a vehicle used on public roads. Oregon State law has similar prohibitions. This includes removing, gutting the cat, tricking the PCM. (IANAL)

Are you in a DEQ zone?

Since you're either a Federal employee or contractor, I thought you should know.

Aug 5, 2021 | 02:55 PM

#20

Madcap

Thread Starter

Junior Member

Joined: Mar 2020

Posts: 57

Likes: 1

From: Oregon

Year: 1996

Model: Cherokee (XJ)

Quote:

Originally Posted by Saudade

Yeah, I'm aware, and I appreciate what you are saying. I am not in a DEQ zone. Luckily for me, I live and work in such a rural area that we rarely see cops, and the postal service can barely put its shoes on in the morning much less do vehicle inspections on POV routes.