Specifically, THAT one:

 

 

If the wires and connections are all good probe #6 at C2 to see if the PCM is bad.

If the PCM is bad it's probably not, the solder connection is probably broken and needs to be resoldered.

 

He said he used a Bosch O2 sensor. Big no no.

 

Forget the o2 sensor it will not cause a single cylinder misfire. Let’s get back to the beginning . You say you performed a compression check but not a cylinder leak down test your black plug leads me to believe this may be worthwhile . I would like to see inside of cylinder 5 now to see if there is oil on the piston or if one of the valves isn’t seating completely or stuck .

 

Pulled the valve cover and rocker arms again.

I think i have a lifter issue. When we were disassembling the rocker assemblies we noticed something odd. We rotated the engine to TDC for each cylinder then remove and replaced each rocker arm set one at a time. Cylinders 1,2,3,4 and 6 when we removed the rocker arms had residual pressure from the lifter and valve springs till the bolts were one or two turns loose. They went back together the same way, once the bolts were snug they needed about one to two turns and a little valve spring compression before the torqued up to 19 f/lbs.
#5 was different. As soon as we broke the rocker bolts they were loose, no residual valve train pressure and when we put them back on there was no spring compression, once snug they torqued up in a half turn or less. Pushrods were in contact with the rocker arm when torqued down, rockers and pushrods were not loose in any way.

is it possible that coolant in the oil (or just dirt) got into the lifters check valve and is causing them to leak off and collapse?
Could high revving the engine “pump” them up enough to run good for a few second till they leaked down and collapsed again and the miss comes back?

I did run run it with the valve cover off and all lifters we’re moving but I don’t know if they were getting the lift needed.

I’m going to get my dial gages back from my father-in-laws house in the morning and check the lift of the #5 valves and compare it to the lift of the others.

Am I barking up the wrong tree or is that normal for hydraulic lifters? Every time I’ve ever put rockers on over hydraulic lifters there was always a little compression of the valve train.
I got a bad feeling it’s a lifter, that means the head is coming off again.

Thanks for everyone’s input so far, greatly appreciated.

p.s. Why are BOSCH O2 sensors a “big no, no”? I looked all over my area and all I could find was BOSCH.

 

Take a close look at the #5 valve spring and valve . If the valve was closed completely there would be no compression of the spring . Fire it up again with cover off and watch closely inspect before starting for broken spring etc ... could of taken rubber mallet and tapped the springs for 5 to check movement etc . I’m tired but trying to help .

 

A (both?) worn cam lobe could also do what you describe (maybe we don't want to think about that right now).

 

I think it's because John said that Fred said that Pete said that Phyllis said that Spot said they don't work right, then the internet took over.

 

^
lol. Exactly. I’m just not used to everyone ignoring the fact that he used a Bosch O2.

 

Originally I thought it could be an O2 sensor problem too, as 4, 5, and 6 plugs all looked a little toasty so Bank 2 had an issue.

However, as discussion ensued, comes to find out he doesn't have a CARB Cherokee so he got no Bank 2.

 

Y'know, you can make a plug look like that if you're burning antifreeze.

Am I a breath of fresh air or what?

 

Your killing me, Dave

I think I can call it a lifter almost definitively.

Here's the rundown.
I think the #5 intake lifter is collapsed. Remember if I rev it up, the motor runs good for a few seconds then it turns back to crap.
So lifter collapses and starts run bad. Fuel pools at the #5 intake and darkens the #5 sparkplug due to it getting very rich fuel mixture from the partially opening valve. #4 & 6 spark plugs get a little dark due to the same pooling fuel making the mix outside the 4 & 6 intake rich. Fuel Trims, O2 sensor and timing go to **** while the PCM tries to fix it. Rev it up and it all goes away for a few seconds because the lifter got pumped up due to the high oil pressure. Lifter collapses again and it all goes to crap again.

I was advised that a partially opening intake valve due to collapsed lifter could cause these horrible running symptoms I'm having AND it would show up on vacuum gage in the form of a "bouncing" needle.

If that last statement holds water then I can confirm the lifter collapsing.
I started the motor and let it warm up. Rev'd it and got it to reproduce running good. vacuum was smooth as glass. loud tick came in and it started running rough, vacuum bouncing all over.
I took a video but its to big to upload.
I hope I'm correct. I want this saga over.
Other than replacing the lifters is there a fix? Maybe thicker oil (I hate that idea) and see if it clears up now that the coolant is out of the oil?

I ordered a new head gasket, intake gasket (HATE replacing 1 week old gaskets) and lifters today. I hate replacing lifter and not the cam, but its only at 52K so its worth it. They should be in tomorrow.

Thoughts?

 

Video please !!!!! I don’t think it’s a lifter or not yet anyways

 

Dave I wasn’t ignoring your advice about checking the wiring harnesses back to the plug at the PCM. I did do that and mentioned it in my OP.
I also opened up my PCM, visually it looked good. I have a strong background in board level electronics and was prepared to see some popped caps or resistors if not burn traces. I resealed it and had no changes.
Both were solid calls to check.

My brother and I are going to pull the head and do the lifters in the morning if I can borrow a lifter removal tool.
with any luck I can report back tomorrow night with good news.