Hey All,
I am hoping i can find an answer to my 1990 jeep cherokee 4.0 shutoff issue, It only occurs about 110 to 140 engine temp.......sometimes it starts right back up....other times it may take an hour before it miraculasly starts. It is then fine to drive and doesnt shut down at all.
Work already Done: Changed coil, new 8mm wires, low resistance plugs, removed cat converter (temp), replaced crank position sensor, replaced cap rotor etc.
I am currently considering a demon coil for higher output but not sure if this will help or not. Any Suggustions?

I don't think the coil is your issue. It should run fine on the stock coil.

Im confused????
Do you loose total power (12 volts)? or does just the engine shut down with everything else still operational?
Sounds like a fuel vapor lock, or sounds like an electrical issue. I cant help you more unless we can get some more details.

Does the engine loose horsepower before it shuts down?
Do you still have a full 12v.
As much detail as possible would be helpfull.

Thanks for your reply, the engine shuts down but all power is still good, motor cranks over, lights all work etc. i was thinking vapor lock as a possiblity as well. Once the engine is at normal running temp it will restart over and over with no issues. It is only when the engine is warming up that this happens. The engine does not stutter....it just simply shuts off in a moments time. once the engine is at norm running temp it runs without issue including restarts etc. when this issue originally happened the plugs were not getting spark (we tested them on the block). Interesting though......the other night it would not cold start.....i walked away slept woke up and it started fine and didnt shutdown through the warmup at all.

Thanks for that low range, i had replaced all these items due to info on these forums in order to hopefully resolve the issue thinking as the jeep was without spark several times this happened.

I was also wondering.........is there possibly an emmissions senor that could be clogged or even a vacume issue of some type that may cause immediate shutdown? I had also changed the fuel filter out as well. I did not change the fuel pump as the previouse owner had said he had recently done this.

Just a thought, possibly the O2 sensor or PCM.
Thinking prob is possibly caused by the change from open/close loop not happening as it should.
I can't think of any other temp related possibilities at the moment.

have you cleaned IAC ever?

For some reason I am thinking bad ground(s) or internally corroded 12 volt wires.

hes not real clear on exactly when it shuts down idle running turning theres plenty off possibilities ya know ...

Thanks guys for all your input, was tied up yesterday and am going through all ur suggestions today......you all are very much appreciated!!

Hey Free ty for that, it happens on both.....running or driving as well as idle. Is interesting.......this morning it started and jumped to 3000 rpm and ran there (cold start)...... i turned it off after it came to running temp and restarted and it went to a perfect idle........i checked the ACI and it was clean.....i cleaned it again anyway......I did notice that thew screws holing the ACI in were both loose however. As it is now already been warmed up it starts and runs perfectly as id there is no issue at all.

I am hoping that isnt the case........taking into cosideration that it only happens while warming up i am thinking a bad ground doesnt sound right. Obly because it shouldnt be dependant on engine temp.Thanks again firestorm

Thanks Tgorden, I have replaced PCM already but am going to change the 02 sensors as soon as it cools down and i can access them.....hopefully this resolves it.

though you sad funs as if no issues ?