The Gnome

Hey all,

I have a 90 XJ 4.0 experiencing power loss while driving or just sitting at an idle. Its very sporadic, only thing the i can relate the symptoms to is when my CPS went bad, just not as extreme. As i drive along it will just start to stumble a bit, (maybe for a few seconds), and then back running fine. I drive 40 miles to and from work and this will happen on and off the whole way. It will also occasionally stall, but almost always when im in reverse. I have had some sort of stalling issue since i bought it 4 months ago, but i replaced the ignition module and it improved alot. The motor has 170,000 original miles on it. Things i have replaced so far are:
TPS
CPS
IAC
Throttle body
Cap,Rotor,Wires,and Plugs
Ignition Module
Fuel Filter
Radiator
New Battery Cables
My next guess was either temp sensor or cracked exhaust manifold, but it does'nt sound like theres an exhaust leak to me. Anyway was hoping someone might have a clue or could maybe point me in the right direction. The problem seems to be getting worse at a slow pace. Hopefully ive provided enough info and any help is much appreciated, by the way, i dont think my XJ would have been running this long without this forum. Keep up the good work.

Cheers

Boomer573

I am new to these Jeeps, however check out my recent thread on electrical problems. Interment problems are the hardest to fix, regardless what you are working on.

Littlethunder92

I had that problem with my 92 and it was the 02

The Gnome

Thanks for the quick responses, I will look into both suggestions today at work.

The Gnome

Went ahead and put an O2 sensor in and took it for a short test drive, seems like it might have fixed it. The true test will be my commute home.

Okpwrlineman

Mine has been acting up with the exact same symptoms. It's driving me nuts! It feels like it's running out of gas to me. I've checked or changed nearly everything! Good luck with yours!

The Gnome

well it wasnt the O2 sensor, its still acting up. Havent checked the fuses yet. Your right Okpwrlineman, it does kinda feel like its running out of gas. I have also searched for vacuum leaks everywhere but cant find any. i think i might change the exhaust manifold gasket this weekend if i dont figure it out before then. i'm almost at a loss. it seems like its getting worse at a faster rate now.

mr baer

Mine was doing that too
Cleaned the O2 sensor on the manifold
Cut the wires to the one on the cat (which actually help, doesnt throw codes)
Reset the ECU - This made the biggest difference
and put a new ground from the bat to the body

runs mint as now

Okpwrlineman

I was curious as to why you think it could be an exaust manifold leak? O2 reading maybe? Does it have a erratic idle also? Mine will idle down to around 300 rpms at a stoplight and then it will suddenly jump to about 1500 and scare the crap out of you! With 4.56s and a Detroit it will overpower the brakes if your not expecting it.

The Gnome

I have read that the exhaust manifold is notorious for cracking, and one the symptoms is high rpm's on initial engine start up, which mine does. It shoots up to 2500 rpms or so when started and then settles down to about 850, and then stumbles betwen 850 and 400 rpms at idle. So i figured i'd pull the manifold to check for cracks and change the gasket while I'm there. Its kinda shooting from the hip but I'm out of ideas and its been a suspicion of mine for awhile, just havent wanted to pull the manifold. I would actually like to redo the whole exhaust, the thing is, it passed smog when i bought 4 months ago so i assumed the cat and O2 sensor were fine.

Also mr baer, when you say reset the ecu, did you just disconnect the battery for awhile and then hook it back up, or did you have to clear codes.

Rushin

could be the problem that i am having. Mine if i am driving steady at like 55mph it will stutter and even backfire from exhaust, feels very violent. Some jeeps came with incorrectly indexed distributor that causes the spark to crossfire in the distributor. There is a TSB on how to fix it, its for 88 model but as it looks its not just the 88 model that had that issue. If you want pm me your email and i will send you the directions on how to make sure you dont have this issue.

mr baer

take your battery cables off and hold them together for 10 seconds, put them back on the battery and then turn your key on and then your headlights on without starting your jeep but I can't remember how long on the headlights think it was 30 sec or something. It clears the codes and deletes the learned fuel map, so if for some reason its learned a bad map, like I think mine did itll come right

The Gnome

I'll try that before I drive home tonight.

jeans

This is a bit of a long shot, but a old wise mechanic taught me this once. Take a hose and turn the water on to just a dribble. Start slowly pouring it around the engine, one area at a time. If you have any vacuum leaks, cracks in manifolds, poor electrical connections, etc, if may reveal it's self, pin pointing a area to look.

The Gnome

yeah, i tried that, i used a water bottle and also tried carb cleaner which i read works as well. didnt find anything. I reset the ecu and also put a new map sensor on today and i honestly think it runs worse.


Learning patience through Jeep ownership.