I have a 98 JGC 5.2L. It looses spark when hot, but very unpredictable. It seems the coil is not getting the 5V signal when this happens. The coil is new, and I also changed the crank sensor (complete pain in the butt!!! I will junk it before I change that thing again). Any advice??

The only causes left as I can figure it is the computer or the coil pick-up. Also, I read a lot of posts about a cam sensor. I am assuming you are speaking of the pick-up?

I have also read about the factory alarm causing such problems. How do I disconnect it to test?

Updates: Been working on it in the rain for a few hours. Here is what I know:
-I have 5V going to the coil pick-up, but can't get any output by checking with a test light.
-I bought a replacement and put it in and still have the same issue...no output from coil pick-up that I can detect with a test light.
-There is nothing else in the distributor that could be causing the pick-up not to work that I know of.
-I checked continuity from the coil to the PCM and was OK. I tried to loosen the PCM bolts to no avail.

I guess tomorrow I will get into the wiring from distributor to the PCM and also ceck the crank sensor, which is also new, for the 5V output. Beyond that, a bad PCM is all I can figure.

If anyone has any ideas please share!!!

Updates #2: Found a bad 20A fuse under the hood. Replaced it and it fired right up. But here's the thing: I have checked this fuse recently when it wouldn't start and it was good. So I believe I have a bad connection somewhere that was causing the intermittant no spark before, and it finally blew the fuse. Now to figure out where the bad connection is...

Thanks for everyone's help...LOL!!! Do I stink or something?

Incase anyone is reading this, I found the issue (I think). Found the rear O2 sensor wire was laying on rear driveshaft. This had rubbed the insulation off the wire, and it was grounding there. Fixed the wire and she's running again....for now. Hope this helps someone out there...

Incase anyone is reading this, I found the issue (I think). Found the rear O2 sensor wire was laying on rear driveshaft. This had rubbed the insulation off the wire, and it was grounding there. Fixed the wire and she's running again....for now. Hope this helps someone out there...

Thanks, good to know before throwing parts at it!

OK...having same problem again. Here's what I have: The crank sensor and the pick-up coil (aka cam sensor) are both giving the PCM the 5V signal. But there is no output signal from the PCM to the coil. The coil has 12V, but is not receiving the alternating ground to make it fire. I have checked the continuity of the wire back to the PCM and its fine. I do have a functional check engine light when the key is turned on. Computer codes are both O2 sensors. But this wouldn't make the PCM not fire the coil right? Do I have a bad computer?

first of all try to erase the codes and if it come back change both 02 sensor

first of all try to erase the codes and if it come back change both 02 sensor

I have done that, and the 02 sensors do come back. But bad 02 sensors would just affect air/fuel mixture and wouldn't cause the PCM to give no signal to the coil correct? Or am I wrong on this?

your right but if the sensor turn ground could affect the pcm i already have this problem on other vehicule so i try to change it before or inspect sensor wire again on both .for sure you have a problem right there

Im running again!!! I found the plug on the bottom of the coil was the issue. I am able to turn the problem on and off, which is good!!! The plug does not snap onto the coil like it should, and you can wiggle it and cause the car to stall. I really don't want to make a homeade plug, and jeep doesn't sell a piggyback, so I am off to pull-a-part in the morning to try to find one. I am not sure it the 4.0 and 5.2 plugs are different or not.