yeti_

I am not a mechanic, but since i bought this jeep a year ago i have replaced leaf springs (pita seized bolt in the frame rail), both motor mount and trans mounts. left U joint. fan clutch and thermostat. and the starter. did all this with just doing searches here and on other forums and youtube. this brings me to present I recently purchased a bafx odb2 tool (mode $6 is a mystery! to anyone knows of write up on how to understand it please let me know) and thats how i found out that my rough idle was linked to or caused by a misfire.

Here is the information i have

1996 Cherokee 4.0 auto 223k
runs awesome (other than the misfire and idle which flattens out after 1000rpm or so) there is some lifter tick but not near what i have seen in videos and it goes away at 1500rpms. (or is masked but the sound of the intake/exhaust) and sometimes completely when it warms up. The vaccum holds between 24-25 at idle peaks at 28 and lowest is 23.8. oil pressure seems strong between 60-just under 80 while driving and above 40 at idle. temperature use to be all over the place it got hot a couple of time but did not over heat. after replacing the fan clutch and thermostat it runs at 195 or under.

codes showing misfire in cylinder 1 (301) and random misfire in cylinders(300)

compression test showed
#1 70psi dry and 80psi wet (so not likely rings or broken rings?)
#2 125psi
#3 130psi
#4 125psi
#5 130psi
#6 140psi
I didn't have a lot of time to do this test so i'll complete another and wet/dry test in all cylinders.

Here is what i have done so far, all pre compression test.
1.) Replaced #1 injector and swapped a couple others just see if it made a difference (it did not) I cleaned the fuel rail and the IAC while i was in there.
2.)Replaced the famous cracked manifold with dorman oe replacement and went ahead and bought a new NTK o2 sensor (and muffler and tailpipe just nice to have all the exhaust coming out of hole.)
3.) pulled cap and cleaned the points and the rotor (lot of build up) bought new plugs (do champions always come gapped at .035?) this is when i did the compression test.

this is where my questions start.
I plan to do another compression test and a leak down test. is it necessary to have the leak down tool? I assume that i can plumb the air compressor directly into each cylinder and listen for the where the air is escaping from question is what psi? any?

I also suspect the timing chain of having slack i would like to be as sure as possible before tearing to that project, I have been told that i can remove all plugs (for ease of spinning the engine) and putting a wrench on the harmonic balancer bolt to check for slack although they didn't explain how much slack. is there a tolerance or should it be taut?

sorry if this was TMI just wanted to be thorough and am serious about getting any advice or links to related threads or write ups. i have read a wealth of thread about misfires but most of the posters report other symptoms or the threads fall off before sound resolution.

thanks in advance for even taking the time to read this.


Update*
Instead getting to work on the Jeep I instead had to drive it 140 miles round trip to get an insurance check up. Funny thing is just before I left I dumped a can of BG 44k in the tank at one quarter tank and fueled up by the time I got to my destination the Jeep was idling almost perfect in traffic... By the return trip little under half a tank it was/is running worse than when I left. All fluids (oil pressure/water temp) were nominal the entire trip. Checked fluids no signs of water/oil mixture.

Likely a little primitive but assuming the leak down shows it is bad valves, can I replace those valves or do I need to replace the entire head?

teamarctic

I would look into the low compression on #1 cylinder. That is way low compared to the others.

Leak down will tell you where you are loosing it. Simple test is like you said is just hook up compressed air and listen to where the air is coming from.