Start with a complete set of ZFR5Ns........
And, what is the cPS output? Is it's harness grounding out when the engine torques?
As I recall the CPS output is about 5-7 volts running, LOL. 0.50 volts cranking. I am sure it is not the problem.
I would not be getting the perfect spark signals I am getting on the primary feed to the ICM and secondary from HV coil if any of those problems existed.
The Matco Ferret engine analyzer would see those issues Bad CPS, wiring, etc) if there was a CPS signal or ECU or wiring problem. The spark plugs are fouled by running too rich on plug 3 and too much oil leaking past the valve seal on cyl 1-2, and now possibly oil in cyl 3. Cyl 4 four was not that bad, not bad enough to miss fire, but it was fouled, BUT the fact is all four plugs were still good enough to not misfire but were showing severe contamination, from oil and excess gas from the looks of them.
I just discovered that NGK has more than one FR5 plug, such joy, seems one needs to also ask for the v-grove FR5.
I am pretty sure that some of the problem is the head, lifters, valve (guide) issues at its EOL )head needs a complete overhaul or replacing, I have one already), and fuel injector issues, and mixing heat ranges of the spark plugs all together.
Old_Man , I already have a 20 year inventory of Renix parts, used and new. Sensors are not the problem here, neither is the HV coil or ICM.
Everything confirms a fuel injector problem, an oil problem on atleast 2-3 plugs, I have had the oil foiling plug problem from badly worn valve guides on 2 cyls with this rig for over 10 years and 70,000 miles, I have run out of snake oil tricks there, LOL.
But now I am sure there may be trash that got into the injectors fuel feed when I had to replace the o'ring seals on fuel feed line QC about 6 weeks ago. That is about when this problem started, but it got way worse this week. Also the very low STFT confirms that the injectors are sticking open or not closing on time, and the ECU is trying to compensate with a low STFT.
Low STFT means the ECU is using less on-time for the fuel injectors than the ECU data tables and algorithms predict to be needed for a new jeep. Thus this says the injectors are fouled and sticking, letting out too much fuel for the commanded on time.
I have about 24-30 new and good used injectors I switch to. Or I can just pull the filter screens, clean them, put power to them and flush them, before I test them to see if they just need cleaning.
I use to Ultrasonic cleaners in the 1970s for cleaning and repairing fuel injectors.
I will swap the plugs, all new V-grove FR5 NGK plugs, and look at #5 and #6 plugs in a day or two, when I have time again. Then I am sure I will need to pull the fuel rail and injectors next. With luck I can it running till cooler weather to swap the head. I'm getting too old for this shit in the summer here.:flamemad: