wewsel

I have been working on my jeep trying to get it back on the road (yes again).I thought everything was ok, so I loaded up the family and went to the store. Well, everything started out ok, kinda slow but ok. Well that all changed as soon as I stopped at the stop sign. It wouldn't hardly move! It was slow about revving, moving, everything. I hoped it was a one time thing but it stayed that way and actually got worse while I was out. I could have rode a bike to the store faster than we made it in the jeep. It would eventually make it up to speed, but 0-60 times could have been measured in minutes. NO KIDDING!!
My wife said she's tired of dealing with it and wants me to junk it. Now if you have seen it, I can't justify junking an xj that at least looks as good as mine.

I have a new cat with less than 1000 miles on it, so I know that isn't it.
I think the flex plate may be the cause of most of my drama, but I haven't been able to drop the trans. to swap it with the one I got at the j/y the other day.

My questions are....

Could anything else make it do this?
Could it be a bad TPS?
I have a code for the downstream o2 shorting to hot, Could that cause what I have been experiencing?
Could the bad NSS cause something like this?
Why, when I had the a/c on, would it not even go above 1000 RPM in neutral? Turning the a/c off let me drive it home, just slow.

I would hate to get rid of my Jeep. I have a sick attachment to it. Even though I have owned it for almost 2 years I have only put maybe 3000 miles on it. It stays broke more than running. But I would love to see it running like I know it could. On the rare occasions it has run good, It has been a blast. I WANT THAT BACK!
Any helpful advice be heeded and tried. I'm at my wits end on this.

4Doors

I'd get that flex plate fixed in a hurry.

mikeXJ1020

Is the flexplate cracked or broken or making any knocking sounds?

89Laredo

If the flexplate is screwed up the CPS will send bad signals. This will cause the motor to run like crap.

I would get the oxygen sensor fixed too.

wewsel

Replaced the CPS a couple months ago because of dying about 20 minutes after startup and not restarting for a few hours... it works good now on that end.
It runs like crap right now even at idle. Sometimes I hear something from the bell housing, especially during starting. Once while replacing the torque converter bolts (they backed out on the P.O. and I replaced them for her), I noticed I could move the flexplate back and forth a couple inches. I haven't been under lately to see if that has gotten worse, I'm sure it has since it's running so bad now. While making my evening walk with my wife, she made me realize exactly how long I have known the flexplate is bad, and how long I have been putting this off. I guess if I want to stop driving the family minivan back and forth to work I need to try to get this done...
This next weekend is my long weekend off (every other Friday, Saturday and Sunday), so I'm gonna try to do some work swapping with a friend who has a some mechanical work needed and the place to do the work. My wife says it's an excuse to get greasy and drunk... Sounds like a party, right?

89Laredo

I would highly recommend fixing the flexplate if its that bad..

The Flexplate is what gives the CPS its signal, and it has to be a certain distance from teh CPS or ignition timing will be all screwed up.

xjinch

Def. not an expert BUT,
I had an 87 Chevy 1 ton with the 350 in it and it made a horrible sound sometimes that made me think it was the flex plate, unfortunatley I ALSO found that the flexplate would move back and forth a couple of inches.....
ended up being bad bearings in the engine... if you think about it the flex plate bolts to the torque converter (wich is connected to the tranny via a SLIP shaft) and BOLTED to the Crankshaft. I have not pulled apart a 4.0L but I would venture to say its the same. This would explain your loss of power. The way I was finally convinced is when I had a friend move the flex plate and I watched the front of my engine and noticed the Harmonic Balancer moving also (connected to the front of your crankshaft). I hope this is not your problem but it really sounds like it. Good luck figuring it out.

rich

If your crankshaft moved a couple inches you had more problems than bearings.

rich

Have you tried shifting it by hand using the shifter when it does that.

xjinch

In my case the Chev 350 still ran, but it ran just like this engine is running, very low acceleration/no power. It will only run for a little longer before the main bearings give out (all the oil holes no longer line up). when your thrust bearings wear out, the crank will shift (fwd and backward) when you rev it up and let it off, and eat the main bearings. I ended up replacing the engine with a short block. (yes you can get the crank turned under, but its harder to find oversized bearings to match.) If the flexplate is moving back and forth, the thrust bearings are GONE. Usually results from excessive towing combined with dirty oil.
My $0.02

mcguyver_xj

well you chenged the cps your fine their but i know 1998 Cherokee had a recall on the Crank Pos Sen and the Cam Pos Sen and i would test your TPS and also any cel's?

test the tps by unplugging attaching a multimeter to it and slowly moving the throttle it should have a slow steady response if it is jumpy you need a new one...also if the front O2 sensor was bad you would have cel and would get some stumbling and hesitations but not all the time you can test the O2 sensor out of the Jeep by attaching a multimeter and heating it up seeing if you get good response followed by cooling it off a little...any questions just pm me