Random inconsistent miss issues

[maxbraketorque]

This is the Viper coil pack conversion, correct? I like the idea except that I hate spark plug wires.

 

[RCP Phx]

Or Jeep KJ...... https://naxja.org/forum/showthread.php?t=1148702

 

[boncrshr]

It may not be CPS, but with 226K miles, I would proactively replace it. Besides that its a matter of testing connections and swapping parts as the others have said.

My advice to anyone with an XJ is to change the CPS and keep the known good one in the Jeep with the tools to change it as well. It is the most likely thing to leave you unexpectedly stuck. I have only had one go bad slowly.

As far as OP, I experienced similar symptoms with a coil pack that went bad slowly over a period of several weeks.

 

[maxbraketorque]

I gapped all the plugs down to slightly less than 0.040", probably sitting at 0.038". And I installed the MSD high performance COP for the 2000/2001. The vehicle is definitely more peppy. Shifts now have more of a hit to them, there is more power, and throttle response is better. But I can't definitively say that the perceived miss at 1800-2200 rpm at higher loads has gone away. I'll have a better idea after my upcoming road trip.

On a side note, I'm not sure why people complain that much about servicing the plugs with the COP setup. It took me 10 minutes to get the COP assembly off the vehicle, but I suppose that's still too long compared to 10 seconds to pull off a plug boot.

So gapping down the spark plugs to 0.037-0.039" and installing the new MSD coil pack definitely improved power delivery, and it feels like its missing less at low rpm higher load conditions. I suppose that the next step is to go back to the prior coil pack or try gapping down to 0.035".

 

[RCP Phx]

Unfortunately MSD doesn't give any electrical data on that coil pack. When I switched over to the Screamin Demon coil with my MSD unit, I tried to find some large gap plugs, I was not able to find any so I stretched my Champions out as far as I could but that was only .047"!

 

[maxbraketorque]

Yeah, I was annoyed by the lack of electrical data on the MSD coil pack. I even called MSD/Holley to try to get the info, but they tech assistant either didn't have any info or didn't want to give it to me. He only said that the stronger spark is achieved by altering the windings, but that's no surprise.

I'm contemplating asking a friend of mine in the Evo business to make me a Prius/Yaris-based COP for the XJ. Those coils actually have a fair amount of kick, but of course it would be significantly more expensive than the Screamin Demon approach. I just hate spark plug wires, and I like how open the passenger side of the engine bay is with the factory COP setup.

 

[RCP Phx]

Yeah, I was annoyed by the lack of electrical data on the MSD coil pack. I even called MSD/Holley to try to get the info, but they tech assistant either didn't have any info or didn't want to give it to me. He only said that the stronger spark is achieved by altering the windings, but that's no surprise.

I'm contemplating asking a friend of mine in the Evo business to make me a Prius/Yaris-based COP for the XJ. Those coils actually have a fair amount of kick, but of course it would be significantly more expensive than the Screamin Demon approach. I just hate spark plug wires, and I like how open the passenger side of the engine bay is with the factory COP setup.

Did you read my thread, I originally tried to do COP but the PCM architecture does not allow that unless can you make a signal converter for it.

 

[maxbraketorque]

Did you read my thread, I originally tried to do COP but the PCM architecture does not allow that unless can you make a signal converter for it.

I had forgotten that was mentioned in your thread. Rather amazing that coil power runs through the ECU. That takes care of Prius/Yaris coils as an option. Did you have any further info on whether the JK coil pack has a different primary winding resistance than the Viper coil pack? Would seem to be pretty important to know if the ECU is handling coil power.

 

[RCP Phx]

There is not a lot of primary resistance difference between a JK coil and the Screamin Demon, I cover that I thought also.