02 Sensor heater circuit fix to cure stalling and PCM symptoms

Howdy ya'll! I have trolled this site for many long nights of troubleshooting and today I realized why the heck do i not have an account here. I have a 97 XJ chop top. AW-4 with np231, cv shaft conversion on driveline from my ZJ, 30x9.5r15 Cooper AT3's, no sway bars, Rancho shocks from a 2 inch lift, angle iron bumpers, 20,000 pound hand operated winch from a IH Farmall M series tractor, otherwise she is bone stock but straight piped. Wish i knew how to upload a pic of it for my avatar. Anyways I have wheeled this Jeep hard for a few years on my land and took it off the street. My lemon ZJ had the VC fail and my front diff carrier chewed apart so i took all the nice stuff off of it and put it on my XJ and got plates and insurance for it. I had just finished a 250 mile highway cruise at 70 mph with no problem. The next day it cut out, check engine light came on. Though nothing of it and it ran fine offroad all day in the snow. The next day, it started bogging out very bad after warming it up and getting it down the road. heavy throttle seemed to be the cure, but it would cut out and then surge while i was on a snowy road in 2wd and i would fishtail all over dodge. I brought it back and tested fuel pressure. it was about 49 psi with engine running. checked compression, everything was within about 5 percent. Pulled 4 month old NGK plugs out, electrode not worn at all but plugs seemed very loose and a few had oily threads, a couple had black carbon deposits everywhere, and two had gunk on the end. Replaced them. No effect on rough idle and stalling. Tested TPS and it had .7 volts at idle and smoothly went up to 3.99 volts at wide open throttle and the input wires had 5 volts. MAP sensor tested fine, so did CKS. I tested the ignition coil by removing the wire to the distributor and put a plug in it and held it like 1/2 inch from the block and it was night time and i saw a nice blue spark. After a bogged out test drive i parked it and it regained life in idle but then after 5 minutes it sounded like it had 3 cylinders lol. i played with the wires going to the PCM and all the sudden it regained full power when i pushed against the the harness connectors. Playing with these wires had a direct effect on engine performance but i couldnt get anything to stay either running good or bad. So i cleaned the pins with contact cleaner and used large cable ties to secure them to the PCM and wedged eps insulation between the fender and air box. Started it up and it seemed good and test drove it several times and made it all over without cutting out bad, just always bogging in mid throttle in 1st, 2nd, and 3rd gear. Flooring it to 5th gear and cruising in 5th, she was just fine. Brought it back and it was idling fine and then started bogging bad. So I started looking in the engine bay PDC and found a blown 15a mini fuse which i learned was the heated 02 circuit. replaced that fuse and check engine light turned off immediately and bogging stopped as soon as the fuse went in. Drove it 30 miles round trip with no problem and let it idle for 10 minutes when i got back and its fine and no engine light. I have a muffler right on the pipe where the cross member is. so there is no downstream 02. my buddy cut the exhaust off late at night when we were drinking on my private land. dont know why i allowed that. so im sure the wires were snipped on that 02. so much snow on the ground in april here in Wisconsin that i have not crawled under to investigate that much. i do know that the 02 wires are mighty close to the exhaust manifold. but the fuse has not blown again yet. I am sure i will need to re route or secure those wires somehow or it will probably happen again. I just thought i would share this for anyone having the infamous PCM symptoms and stalling. And maybe i could get some input on some things to do to correct any future wiring issues likely to occur. I am glad to be on this forum and look forward to taking part in all discussions with troubleshooting, custom building, etc. Im enrolled in the fall semester for Auto Tech and can't wait to master these jeeps and learn how to upgrade the many flimsy components Chrysler master minded after their engineers took too many magic mushrooms

O2 sensor wire attacks are common on the old Renix jeeps as well, the front drive shaft, the steering shaft, and the exhaust manifold eat the O2 sensor and the CPS wires with ease. Rough running at idle is a common sign. The newer vehicles have issues with the O2 sensor wiring when exhaust work or custom work is done that leaves the wires dangling loose for road hazard stuff and hot pipes to damage them

Here is an update after 2 days with this problem fixed. I did end up blowing the heater circuit fuse again, so I bit the bullet and laid in the snow/ice/mud/crud to confirm what I had already pretty much knew...4 snipped wires laying on my rear driveshaft rubbed all the way through. I cut them back to their connector clip and cut the wires completely flush, and then rtv and a heavy application of elec. tape wrapping around the whole connector and then some hot glue and zip tied that deal far away from the shaft. Did a couple of 20 mile trips today, and went off road through some snow covered high flexing terrain just creeping in 4lo. Never had a problem all day, no engine light. Didn't skip a beat. I also cleaned the IAC and Throttle body out squeaky clean so today I enjoyed the best performance out of my Jeep since I have owned it. It was a great feeling. Didn't have beer to celebrate with so I settled with a pot of coffee :tear:

So EcoMike are you a bigger fan of the older renix or the newer style like I have? Im still new on it. I know their is throttle body and the HO multiport injection but I still had to go over my Haynes manual to make sure what I had in mine.

In general I like the simplicity of some older stuff, but the fuel injection that came out with Renix is and was an awesome improvement over carburetors. OBD-II since 1996 is awesome in man ways I prefer fewer O2 sensors, fewer cat converters, and less complex diagnostics. Not a huge fan of air bags, and I like the closed Renix cooling system, they just need a better coolant bottle than the junk from China. I started driving my girl friends 96 Cherokee and fell in love with them, then bought my 85 non Renix diesel FrankenJeep, then later the 87 Renx Wagoneer and so on. I just know the Renix system top to bottom so it is easy for me to diagnose issues before they are a real problem. Many things on the HO's I am not up to speed on. Also I have 15 years of salvaged Renix parts in my stash now for retirement LOL:laugh3:

One thing I really like about Renix years, 87-90 is the hot dip galvanized steel body, that still has no signs of rust here. The new stuff is no where near as good, electrophoretic coatings.

Yea I know well how Jeep likes to have some super reliable designs some years and then come along with something really flimsy for a particular model. Like you, I always seem to prefer what I have already memorized in the back of my head.

On another note, I am now running with great performance, but I still have a straight pipe and only an upstream 02 (I know some folks frown upon this, but I live in northern Wisconsin, no emissions and people drive mud trucks and 44's on the street everywhere) sooo I wonder how long it will be before I get a check engine light from no cat. I am surprised that I have ran it a few days on the highway and offroad without the engine light appearing.