So I have no idea what's going on. My XJ ran just fine about a week ago when I drove it last. Here is a YouTube video I made about what the issue looks like: https://youtu.be/uJZE5K07EB4. Anyways it will not idle at all. Whemever I lift my foot from the pedal, it sputters and idles at only about 200 rpm for a few seconds and then the voltage gauge goes down to about 10v. After that it either shuts off and dies or it revs back up to normal idle speed and the voltage goes back up. It seems to drive perfectly fine whenever I have my foot on the pedal. Later on today the voltage gauge read 0 and the Check Gauges light turned on. A few minutes later the light shut off and the gauge started working again. Could this be a case of a failing alternator? Also, I have to jump start it every single time I start it because it won't even crank when I turn the key

 

From the symptoms, it would appear that your system voltage is low at times. This can lead to the kind of strange starts where failure to stay on the pedal leads to stalling. This type of problem can be caused by a failing battery, a failing alternator, and most commonly poor connections. I would start by cleaning up the important electrical connections, including the ones to the alternator. I will include a video to help point some things out. This is also the time of year where a marginal battery is likely to give up on you (as things get colder). So do the connection clean up, but don't be surprised if the battery is weak as well. A failed alternator is a possibility, but less common than the other two possibilities. After cleaning up the connections, you can take the vehicle to have it load tested (test of the battery and alternator) at most major auto parts stores. This test typically requires at least one restart, so if you have concerns have a friend follow you there with jumper cables.

 

Thanks a lot for the reply! I re-did a lot of my wiring about a month ago so it's all clean. I'll have to make sure all the wires are tightened down though. I do have a really cheap battery in it that came with the Jeep when I got it during the summer. I have a spare battery I was going to test today, but I ran out of time before it got dark and started raining. Im hoping it is the connectors that are messed up, but if not I hope its the alternator. I was planning on getting a 130A alternator from the salvage yard tomorow anyways because I have a lot of accessories to power. Thanks again for the reply!