Talk me down. Just Empty Every Pocket

I really love my 96 XJ. Drives nice, quiet, 20+mpg combined, a machine in the snow, fits all my winter gear. 

Last week the clutch master, slave and TOB went out. I'm not doing that in the snow in the parking spot of my rented room with minimal tools so I paid a shop to do it. 

Since I've owned it there has been an inexplicable 3000rpm rev limit. As of two days ago that's a 2000rpm rev limit. This morning it started missing and sputtering and died on my going to work. 

I managed to get it fired back up and went to a shop that my supervisor recommended. They're a diesel shop but all the mechanics are Jeep guys. He drives a tired '94 ZJ and trusts them. 

I'm just fed up. I don't want to lose this Jeep. It's a really solid body. Suspension has been refreshed. Heck, a tow truck driver tried to buy it while he was towing it. Plus the aforementioned clutch refresh. But at the same time, I don't want to keep pouring money into it without getting somewhere. I've got ~$5000 into it including buying it, parts I've installed and work done by others for a total of 33000 miles driven. It doesn't help that I'm 3500 miles from my garage, tools and other car. I can't think of another vehicle that would do everything this one does for this price point that wouldn't also take work. 

$5000 for 33,000 miles is not bad. That's $.15/mile. I suspect you're well below average at that point.

Sell it. Get a 4 Runner. 

Does a check engine light come on when the engine bounces off its fake rev limit? If so, what codes are you getting?

XJ that you’ve done goog maintenance on?  IIRC that clutch shop said it needs a cat.  I’d replace that and be good. Sounds like you’re selling at the wrong time. 

The false rev limiter is likely some single point failure that's likely a fixable external item.  

Ignore the sunk cost fallacy.  

Get it properly diagnosed and then do your cost to fix analysis.  It otherwise does everything you want it to do, and sounds like you still love it.  Just get it fixed.  

Didn't you say in your other thread that it had a plugged cat?

That would be your rev limiter right there.

ShawnG said:

Didn't you say in your other thread that it had a plugged cat?

That would be your rev limiter right there.

And my next check after that would be a crank position sensor, maybe a cam position sensor if it has one. 

How many stickers are on it? If there are more than 2 jeep decals or stickers (it's a jeep thing, jeep life, just jeep it, only in a jeep, got mud, if you can read this flip me over, etc) I vote you keep it on the road regardless of costs. If 2 or less, than you obviously are not deeply involved in the jeep life and will realize how horrible they are as daily drivable vehicles once you have even a somewhat livable alternative in the driveway. 

The problem you describe is screaming failed catalytic converter.  The honeycomb structure inside can break which means you now have a sideways honecomb... also known as a wall.

Quick and dirty test.  Pull the upstream O2 sensors and let them hang.  Do you now have a 2500 rpm top end?  Bingo.  Cats.  Replace and keep on driving.

If that doesn't pan out, look hard at fuel pressure.  A failing pump or clogged fuel filter will present similarly.  It has enough flow and pressure to keep up until it doesn't.

I have a 94 Mazda B4000 that has all kinds of problems and it's frustrating, but it's low miles, rust free, and cheap.  I'm not selling it.  I'll keep fixing it because I love it.

Not selling it, just angry at it. I'm well aware of sunk cost. Plus, I'm not going to pay the Toyota Tax. The two mile walk to the bus depot helped clear my head. Not saying I wasn't dreaming of stuffing a small block under the hood.

Plugged cat explains rev limit but doesn't explain the ignition cutting out or the P0351 code. Being a 96 that code only means "misfire." I wanted to diagnose more myself but I was laying in snow in -5° wind-chill. 

It has had 4 different crank sensors and 2 cam sensors in 2.5 years, still 3000rpm rev limit after each replacement. Also IAT, MAP and TPS replaced with known good units. Had a shop oscilloscope and resistance check the sensors, all of which tested well. It has a new fuel pump, sock and filter. I also swapped to another 96 4.0 ECU and the symptoms didn't change. 

It definitely could explain the misfire code.  Exhaust can't get out, cylinders start misfiring.

Many times a collapsed catalyst won't set a code.  The exhaust is still flowing over the catalyst, so the downstream sensor doesn't get any crazy information saying it isn't working.  You usually get a P0430 code when the catalyst is spent, but often don't get a P04xx code when it physically breaks.

If you've done all those parts (and they are still testing good) I would strongly look at the catalyst.  Winter car work sucks, but see if there is an easy place to make an exhaust leak that is upstream of the catalyst and see if it changes.

All it needs is to be diagnosed and repaired correctly. Any car regardless of price can have difficult issues pop up.  I'd just try to squash my impatience until it's fixed and see if you ever look back. 

THIS is a 4.0 Cherokee and while this is a different setup with a different symptom, it's a good example of someone doing some fairly high level diagnostic work. You just need the right person to make your problem go away. 

Luckily my patience is high. My landlord and I work together and have the same schedule so I have a ride to work every day. Only have to have it fixed by April to drive back to NC. 

Here's the video I took of the rev limit

https://youtu.be/_6a1b4If4tY

Would it be cheaper to sell the busted XJ and buy a better one? Might be worth pricing it out if the cat fix doesn't pan out. Good luck! I've always wanted an XJ, despite driving cross country in one in the 90s.

Video doesn't look like a cat issue. Looks electrical to me. Wish I was local to help. 

I still think it's the catalyst.

I would yank the upstream O2 (or find another way to make a leak before the cat) and retest.  Given all that you have replaced, another quick and dirty test would be to find another ECM and plug it in.  They don't fail frequently, but sometimes they do, and they cause all kinds of stupid issues.  I'm just thinking it could be an easy test that you could do with a buddy's ECM, or reach out to a Jeep forum to see if someone would lend you one.

Dave M said:

Would it be cheaper to sell the busted XJ and buy a better one? Might be worth pricing it out if the cat fix doesn't pan out. Good luck! I've always wanted an XJ, despite driving cross country in one in the 90s.

At this poing on XJs, he knows this one no matter how broken it is. The rest of the XJs are old enough that are plenty of chance that any other XJ will havr a similarly annoying issue pop up not long after purchase. If he still likes this one I'd stick with it.

I also vote cat. Literally just fixed the same issue on my Saturn. It presented itself with a part throttle misfire when cruising in 4th, a refusal to pull itself in 5th and an unwillingness to rev past 3500rpm. Took care of the cat and it's back to normal with all of those symptoms gone. All of the catalyst material was busted loose and shifted sideways.

Didn't you post a photo in another thread of you holding chunks of catalyst material? If so, you know almost certainly that the cat is plugged up. Get that out of there and then worry about how to fix it if it's still acting up.

5 minutes with a sawzall will verify the problem.

Yeah... This thread.

Dude.  CATALYST.

Lol, i didn't see the other thread has been updated with actual chunks of catalytic converter!! Yeah, might as well get that straight first before doing anything else! 

i think we're all missing something obvious here.  has anyone suggested CADILLAC CONVERTER?

CATTYLACK CONEBERKER!