wolffjeepie

hi! im in need of some serious help. I have a 2000 jeep Cherokee sport 4.0l and I am desperate. I bought the jeep 4 months ago unaware of a misfire issue. I started by replacing spark plugs and oil change when I first got because unaware of last time it was done. about a week later I went to go pick up a new coil rack and got stuck in the parking lot. changed fuel pump and it was not the issue. changed coil rack and it still would not start. rolled it to the shop next door after a whole day in the parking lot trying to figure it out. 950 later and 4 hours of diag and it was a grounded wire. picked up the jeep 2 days later and it was misfiring in cylinder 4 and 6 was able to still drive it. it was a slight misfire. a week later jeep acting up again with massive misfires.put the oil coil rack back on and it was only slightly misfiring. couple days go by still acting up pulled spark plugs and one was cracked replaced the cracked one and burned on. was running and driving fine with small misfires. I could delete the codes and it would drive just fine. few days after that replaced crackshaft sensor thinking maybe that was the problem nope didn't fix it. more time passed changed 3 fuel injectors 4,5,6 still acting up cleaned throttle body ran cleaner through and still having the issue it will go from cylinders 4 and 6 to 3 and 4 1 time it was 1 and 6. at one point I turned it on to go to work and engine light was flashing idle rough and I turned it off and took my wife's car to work. recently i have not been able to drive it because on the way to work it would shake bad and shut off on the highway and it happened 3 times within 20 mins finally half way to work I gave up turned around to head home and it did it 4 more times trying to get home and it has sat for 3 days now because I'm at a lost.
so far changed:
crackshaft sensor
spark plugs
coil rack swapped back and forth between new and old and it ran better with the old one
oil changed twice
fuel pump
3 fuel injectors
battery
alternator
throttle body cleaned
someone please help me give me ideas to look for
also already told about cylinder 2 low compression but hasn't show any problems

Saudade

How "low" was #2? I suggest you do a compression test on all 6.

What specific codes are you getting?

wolffjeepie

p0304 & p0300 & p0303 or when it randomly switches it goes to p0300 p0304 & p0306

but it’s never been cylinder 2
mechanic said it was at 40

awg

hard to tell whats wrong.

I agree a compression test is tneeded

I would also hook up a manual vacuum gauge, as that will give many indications of internal engine faults

If it isnt internal, you may have an issue as simple as the main ground for the PCM, wiring harness issues, or the PCM itself

The PCM ground is a nut on stud on engine, the harness that goes tight around the intake manifold is known to wear and the wires touch, I think its the injection harness, you would need to unwrap the tape and inspect the wiring

Saudade

Well, this seems rather irrelevant now. 40 PSI is waaayyyy to low. You said you knew about this before you bought it? What are the readings from the other cylinders?

awg

What he said did not make sense to me, no mechanic would proceed with a 40psi reading on a cyl ? (unless they were just stealing money)

A blown head gasket or cracked head could be causing all issues.

That has to be conclusively ruled out before anything else is done

look inside the oil filler cap for creamy residue, I have always found that is a consistent first warning