I have been having been having misfire codes for about 9-10 months. So I swap out all the spark plugs (Champion coppers), and distributor and the down stream O2 Sensor. (I have the up stream one ready to go in). it has had a rough idle for a while along with these misfires. For the most part the motor seems to work great in the high RPMs (1750+).
Today it shut off on me while I was driving it. I had a loss of power and I hear a big pop. A buddy who is a better mechanic than I pulled me into a parking lot and he checked on some things for me. We tried turning it over and it cranks good but no start. He unplugged one of the spark plug wires (cylinder #3, We later tested Cylinder #2 to see if it was a valve issue) and we turned it over and It started. I'm no mechanic but I found it odd for it to be able to start like this.
My friend said that it could possibly be a timing chain issue, however when I purchased the jeep I needed to replace the motor so I decided to do some maintenance before putting the new used motor in. Is it possible that the timing chain has skipped a tooth?
I'm at a loss here as most videos/forums seem to be distributor/spark plug related. Willing to spend money on fixing it but every thing I do to it seems to fix nothing.

 

I think you are starting to experience the classic crank position failure. Most of the time they just sort of start to fail, runs great most of the time, but rough running and maybe pull up to a stop sign and stop running and then start up when the engine is cool. I would be willing to bet it has never been changed. By the way the upstream O2 sensor is much more important to running right than the downstream

 

Thanks, I'll look into the crank position failure and throw the O2 sensor I got on it. Just got it towed to the house so I can start to work on it.

 

Good luck

 

Get yourself (or borrow) a scan tool that can show the TPS output graphically, and see if it's steady at idle, and has smooth response with no dead spots. Check it while driving, too (you may want a helper for that, to be safe). Mine ad similar issues, and seemed ok in the garage, but the output signal was all over the place while driving at any speed. My CPS was bad, too, and had been replaced just before the TPS was checked while driving. Mine runs GREAT now!

Hope that helps!

Eric