Starting problems in my 2000 XJ
 

For a while now, my 4.0L 4x4 XJ has had issues starting, so far in my attempts to fix it I've replaced the Crankshaft Position Sensor and the Idle Air Control Valve, it seemed to have worked for about a week, now it's not starting again, it's even worse than before. I've noticed that when it does start it'll idle around 200-300 RPM's and the battery gauge will be at zero, any advice is welcome, thanks.

you did not mentioned engine check light ? no codes ? might want to research these issues on your ignition system. If you still have a distributor do the simple stuff like pull the distributor cap and check the rotor. New plugs ? are they all firing?

Try the coil pack.

The engine check light hasn't come on, and I'm fairly new to this so I'm not sure how to find codes, if it's with a scan tool, I don't have one of those. My best guess now is that it's the Throttle Position Sensor.

Did you use a mopar cps? If not, your new cps could still be at fault. +1 on checking the coil pack.

Also, what voltage do you read across the battery when it's running?

I recently discovered that I have a bad cell in my battery, so that's probably going get replaced soon, I'm assuming it's the culprit of my starting issues. I'm fairly certain it was a mopar cps, I might replace my maf sensor within the next couple of days only because it's the only thing on the throttle body i haven't replaced so far.