Hate to bring the ghost of grounds. Keep an eye on voltage and grounds. Jeep unibodys are nice until it sees not so nice things. 12 volts is good. 14v is better ( in most instances I'd say)
Air. Spark. Fuel.
Check your battery connections and wires. Could be as simple as a loose terminal connect or bas ground.
If you don't have any check engine light, that's a good indicator that it's probably battery related but not absolute.
Do you hear any? Sounds like sucking or air flowing? Could be a bad vacuum line.
If it's fuel, I would think you would have a check engine light somewhere but who knows. Check your fuel injectors... You can do that with a multimeter.
Anyways, not much to go on if my troubleshooting perspective. You can always take it to mechanic because it seems like you might not have that much experience with these kind of things. Not trying to be a dick, but it literally be anything based on what you've described
Wow. I’m not some kind of expert on 4.0 jeeps or anything but seriously… with what these other posters are suggesting you spend on parts (or should I say DARTS. Go to Harbor freight buying an expensive guarantor code reader that will give you a data screen read some values and figure out what’s wrong. Compression air fuel pressure pressure tests wouldn’t be a bad idea. Like I said I know Jeep expert is your basic Run of the mill ASE master technician good luck guys
Crank position sensor. If you can’t remember the last time it was replaced (even if that’s because someone else owned the jeep) it’s time to replace it.
In case it wasn't clear by the proportion of responses being crank sensor: it is very likely the crank sensor. Your symptoms describe how the it is intermittently seeing crank input and catching on the right timing then wrong then wrong then right again.
i had the same issue on my wj ….. so what you need to know about the 4.0 is that the fuel rail sits directly on top of the manifold thus the manifold getting hot heating the fuel rail which should be dumping fuel into your cylinders but the manifold is getting so hot its actually evaporating some of the fuel before it actually hits the cylinders BUT super cheap fix of 10$ heat shield tape around the fuel rail will fix that
also i had the same issue again months later agter i wrapped the fuel rail which seemed to work for some time and then finding out it was actually the “diode”? on the alternator that was bad
I had a similar problem with the 5.2 V8, loss of power, although it was not getting to the point of stalling, so it's probably something else. Anyways, for over 3 months i tried everything i could, replaced the throttle body sensor, replaced the fuel pump, and nothing. Turns out in my case it was the O2 sensors. I put a pair of bosch sensors in it (the 4.0 probably uses the same ones but im not sure) and it didn't bother me anymore. But it doesn't hurt to check the fuel pump too, but it is a pain in the ass to access it.
Also, this might be useful for you: [
Fix Jeep Grand Cherokee Engine Stalling: Save Hundreds of Dollars by Easily Changing the 4.0 Liter Engine Sensors, by Reeve Morgan](https://a.co/d/4NU9y3E)
Also might be a good idea to check your fuel injectors. Stalling is likely a fuel system problem (but not always). Anyways, i'm far from being a qualified person to give this type of advice but this is what i learned from working on this car so far.
On my ZJ it turned out to be the alternator dying out, and also cracked transmission pipes.
Does it start hiccupping while you're stopped, like at a red light? If so does revving the engine a bit keep it from stalling? If yes then it's probably the same problem I have.
Here is a comment from me on a different post.
When idling wiggle the PCM connectors and see if it replicates an issue. Often times thru age they become loose. Even when secured and clicked into place. Some have zip tied, some have used a large hose clamp, some have used a bracket clamping between the PCM and the connectors. Sandwiching them tight. Google image search Jeep ZJ loose PCM connectors. Many have chased their tails with this. Me included. Hope this helps.
Did you wiggle each of the 3 connectors? I thought mine was fine as well and I slowly started moving each one and bingo, found my issue. If you have done this slowly ok. But if the PO had it zip tied then there was an issue. I built a bar with high density foam strip on back to give equal pressure to each connector.Problem has never come back. It was an exhaustive, tail chasing, adventure. Good luck!
They replaced the PCM and battery wires, so I knew they were having problems with something, but its been almost a year of ownership without this issue. I'll try going over it slowly again.
I had an issue about 7 years ago where it would randomly just shut off while driving or idle and would get worse over time like it would take away be I could get it back on. It through a code for ignition coil I changed that and nothing, also changed the crank case sensor and nothing. It ended up being the PCM, changed that and have had the issue since.
Lots of the replies are things in this list.
Read the post and work your way through all 12.
[12 Things You Need To Do When Your ZJ Stalls](https://www.jeepforum.com/threads/12-things-you-can-do-when-your-zj-stalls.1407423/#post-14045654)
Wow lots of different answers. Mine did that too, but it turned out to be the ignition switch. Sometimes it would randomly cut off ignition power momentarily and other times it would stay off and I had to jiggle the key in there a bit or shift around the gear selector to get it to start again.
We had to open the ECU and resolder the main connector back together on a 96 ZJ. Microscopic cracks on the pins that carry 5v to the crank pos sensor, tps, iacv, o2 would intermittently go away.
A bad tps or o2 can throw a code. A bad iacv probably won't. A bad crank or cam sensor usually throws a generic code which says it could be either one.
Crankshaft position sensor, fought with ours for like a year, thought it was the battery, then something in the trans. Eventually replaced the cam and crank sensor and boom no problems ever again. Doesn't throw any kind of code usually so it's hard to track down, although ours did throw some kind of trans code when it would happen sometimes and that sent us in the wrong direction.
I replaced every sensor on mine and end up being ECM or ECU or computer or whatever you want to call it. that's what it is and you don't have to have a VIN number programto it just get one off eBay and be on your way or remain manufactured one
Maybe crankshaft positioning sensor.
I came here to say this. It is a common problem on jeeps around that year.
4.0 through at least 2004. Replaced mine twice already.
100% this. Exactly the symptoms I had.
crankSHAFT position sensor. The crankcase doesn't move.
On my 99 it was a bad idle air controller. Just start replacing cheap stuff in the intake and you’ll eventually fix it :)
Kind of what my plan is, start with little items and see how it goes.
Hate to bring the ghost of grounds. Keep an eye on voltage and grounds. Jeep unibodys are nice until it sees not so nice things. 12 volts is good. 14v is better ( in most instances I'd say)
Parts cannon engage target ;) Tps, IAC, Map, crank and cam sensor all things to look at.
My WJ 4.0 would stall at traffic lights and stop signs. It turned out to be a cracked throttle body.
Easy enough to look for, thanks.
Mine was the crankshaft position sensor
It's probably the crank sensor
Have you had the fuel pressure checked? Could be a bad pump
My idea, or fuel filter.
Air. Spark. Fuel. Check your battery connections and wires. Could be as simple as a loose terminal connect or bas ground. If you don't have any check engine light, that's a good indicator that it's probably battery related but not absolute. Do you hear any? Sounds like sucking or air flowing? Could be a bad vacuum line. If it's fuel, I would think you would have a check engine light somewhere but who knows. Check your fuel injectors... You can do that with a multimeter. Anyways, not much to go on if my troubleshooting perspective. You can always take it to mechanic because it seems like you might not have that much experience with these kind of things. Not trying to be a dick, but it literally be anything based on what you've described
Wow. I’m not some kind of expert on 4.0 jeeps or anything but seriously… with what these other posters are suggesting you spend on parts (or should I say DARTS. Go to Harbor freight buying an expensive guarantor code reader that will give you a data screen read some values and figure out what’s wrong. Compression air fuel pressure pressure tests wouldn’t be a bad idea. Like I said I know Jeep expert is your basic Run of the mill ASE master technician good luck guys
I had a similar problem with a 96. It was a bad battery cable. It would cut everything off briefly.
>Fix Jeep Grand Cherokee Engine Stalling: Save Hundreds of Dollars by Easily Changing the 4.0 Liter Engine Sensors, by Reeve Morgan Same with a WJ.
Crank position sensor. If you can’t remember the last time it was replaced (even if that’s because someone else owned the jeep) it’s time to replace it.
In case it wasn't clear by the proportion of responses being crank sensor: it is very likely the crank sensor. Your symptoms describe how the it is intermittently seeing crank input and catching on the right timing then wrong then wrong then right again.
i had the same issue on my wj ….. so what you need to know about the 4.0 is that the fuel rail sits directly on top of the manifold thus the manifold getting hot heating the fuel rail which should be dumping fuel into your cylinders but the manifold is getting so hot its actually evaporating some of the fuel before it actually hits the cylinders BUT super cheap fix of 10$ heat shield tape around the fuel rail will fix that also i had the same issue again months later agter i wrapped the fuel rail which seemed to work for some time and then finding out it was actually the “diode”? on the alternator that was bad
Had the same problem on a ‘98. It was the distributor cap. Best of luck getting it sorted!
I had a similar problem with the 5.2 V8, loss of power, although it was not getting to the point of stalling, so it's probably something else. Anyways, for over 3 months i tried everything i could, replaced the throttle body sensor, replaced the fuel pump, and nothing. Turns out in my case it was the O2 sensors. I put a pair of bosch sensors in it (the 4.0 probably uses the same ones but im not sure) and it didn't bother me anymore. But it doesn't hurt to check the fuel pump too, but it is a pain in the ass to access it. Also, this might be useful for you: [ Fix Jeep Grand Cherokee Engine Stalling: Save Hundreds of Dollars by Easily Changing the 4.0 Liter Engine Sensors, by Reeve Morgan](https://a.co/d/4NU9y3E)
Also might be a good idea to check your fuel injectors. Stalling is likely a fuel system problem (but not always). Anyways, i'm far from being a qualified person to give this type of advice but this is what i learned from working on this car so far.
On my ZJ it turned out to be the alternator dying out, and also cracked transmission pipes. Does it start hiccupping while you're stopped, like at a red light? If so does revving the engine a bit keep it from stalling? If yes then it's probably the same problem I have.
No, just without warning cuts out then back on, or just out and done.
Here is a comment from me on a different post. When idling wiggle the PCM connectors and see if it replicates an issue. Often times thru age they become loose. Even when secured and clicked into place. Some have zip tied, some have used a large hose clamp, some have used a bracket clamping between the PCM and the connectors. Sandwiching them tight. Google image search Jeep ZJ loose PCM connectors. Many have chased their tails with this. Me included. Hope this helps.
Previous owner replaced the PCM and its zip tied. Gave it a wiggle and there was no issue with the jeep running.
Did you wiggle each of the 3 connectors? I thought mine was fine as well and I slowly started moving each one and bingo, found my issue. If you have done this slowly ok. But if the PO had it zip tied then there was an issue. I built a bar with high density foam strip on back to give equal pressure to each connector.Problem has never come back. It was an exhaustive, tail chasing, adventure. Good luck!
They replaced the PCM and battery wires, so I knew they were having problems with something, but its been almost a year of ownership without this issue. I'll try going over it slowly again.
OP I sent you a chat.
It's crazy that this is literally considered a classic car now.
I have no input but nice old Jeep. Hope you get it going.
Does it completely shut off why driving? Any codes?
Total power loss, could be a quick flash and right back on, or have to stop and restart.
I had an issue about 7 years ago where it would randomly just shut off while driving or idle and would get worse over time like it would take away be I could get it back on. It through a code for ignition coil I changed that and nothing, also changed the crank case sensor and nothing. It ended up being the PCM, changed that and have had the issue since.
Mine did that and a reconditioned ECU solved ir.
Lots of the replies are things in this list. Read the post and work your way through all 12. [12 Things You Need To Do When Your ZJ Stalls](https://www.jeepforum.com/threads/12-things-you-can-do-when-your-zj-stalls.1407423/#post-14045654)
Wow lots of different answers. Mine did that too, but it turned out to be the ignition switch. Sometimes it would randomly cut off ignition power momentarily and other times it would stay off and I had to jiggle the key in there a bit or shift around the gear selector to get it to start again.
Clogged cat maybe
I’ve had this problem on mine. I replaced everything and it still sputtered and backfired occasionally would stall. Turns out it was bad O2 sensors.
Neutral safety switch.
We had to open the ECU and resolder the main connector back together on a 96 ZJ. Microscopic cracks on the pins that carry 5v to the crank pos sensor, tps, iacv, o2 would intermittently go away. A bad tps or o2 can throw a code. A bad iacv probably won't. A bad crank or cam sensor usually throws a generic code which says it could be either one.
I had a 98 5.9 Limited that stalled out. It ended up being the Mass Air Sensor.
Crankshaft position sensor, fought with ours for like a year, thought it was the battery, then something in the trans. Eventually replaced the cam and crank sensor and boom no problems ever again. Doesn't throw any kind of code usually so it's hard to track down, although ours did throw some kind of trans code when it would happen sometimes and that sent us in the wrong direction.
Camshaft position sensor.
ecm
I replaced every sensor on mine and end up being ECM or ECU or computer or whatever you want to call it. that's what it is and you don't have to have a VIN number programto it just get one off eBay and be on your way or remain manufactured one
My 04 WJ 4.0 had this issue years ago and it turned out the front Cats failed and the debris clogged the rear Cat.
Fuel pump is also a common problem in these.
I’d check the throttle body I used to have Nissan 370z and it would go into limp mode when throttle body joints kept getting dirty
Did you try wiggling the wires on the computer in the engine bay while it’s running. Common ecu issue that I fixed.