Missfire, bucking, and surging on startup runs great otherwise

I've got a 97 4.0 175k miles aw4 trans and like the title says as it's acting wild. If i let it warm up for 5-10 minutes it runs amazing but if I try and drive it cold, it feels like the whole drivetrain is about to come loose. This started after my last major tune up, I changed the timing chain, but it's dead on and running great once it warms up. I'm running a summit tune up kit and autolite platinum plugs, just replaced the upstream o2 sensor,new injectors cps is less than 3 months old, all new exhaust, no vacuum leaks to be found, all gauges work, alternators charging at 14.3 and battery is holding at 12.8. The only thing i've found wrong is some slack in the distributor. I should also note that when this problem first started I had swapped from the summit wires to a new set of napa premiums and managed to fry my coil on the way to work. After putting the summit 8mm wires back in it It ran great for a couple of days until it got cold again now it's almost undriveable unless i leave it idling for 15 minutes. I've got a new distributor, accel cap and rotor, and some new taylor thundervolts in the mail and a new set of copper plugs I'm about to throw in it. Aside from that i'm completely lost. Sorry for the long post just trying to lay out all the details I can.

The symptoms suggest an O2 sensor issue. Have you checked the O2 sensor fuses and inspected their wires and wire plugs ? Did you install a Bosch O2 ? The Jeep 4.0L and Bosch O2 sensors do not play well together. Are all the OBD engine sensors genuine Jeep ? You should be using Champion copper plugs or a basic NGK.

Sounds like a distributor indexing problem. Verify by putting the engine at 14BTC, then pull the cap and the rotor should pretty much be on the #1 post in the cap.

If that is fine, I would double check the timing chain.

ntk o2 sensor, the fuse, is good, the cps is from the dealer, everything else is factory as far as I can tell. I just checked my compression and checked for spark, 130ish across all 6 but my spark seems weaker than what it should be. I also noticed my interior lights/gauges/and radio have a flicker to them, I'm starting to wonder if I dont have a bad ground some where. Guess it's time to pull out the ol fluke and start poking around.

old_man said:

Sounds like a distributor indexing problem. Verify by putting the engine at 14BTC, then pull the cap and the rotor should pretty much be on the #1 post in the cap.

If that is fine, I would double check the timing chain.

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My first thought was the timing chain, but once i'm on the highway I can romp on it and it'll never miss a beat. I even put it in neutral and bounced it off the rev limiter and it acts just like I wanted it too. The more i think about it, the more I think this is electrical. The previous owner was a butcher when it came to wiring, I even found an immobilizer under the dash installed with wire nuts.

If you have NTK O2's and Jeeps sensors, then checking the charging system and wires would be my next suggestion, especially since you mention the previous owner butchered the wiring.

I found the problem, the ecu ground had corroded at the back of the block and had was registering a little over 6 ohms at the ecu pin. I re pinned the ecu and ran a fresh ground straight to the frame. I also replaced the ground going from the battery to the coil mount it was reading about 4.5 ohms. It fires right up and idles like it should. I guess it was just a coincidence this happened shortly after I did my tune up, or I broke the corroded wires while I was working on it, either way it seems to be running fine now.

Good deal.

When your distributor slack becomes too much, it'll run fine but stall intermittently when hot.