Jeep Misfire problem

[Wallace's]

Sounds like you installed your compression tester incorrectly on #1 cylinder (would be the only logical explanation to go from 0 to 60psi without "doing anything").

If you have good compression, then that leaves, air, spark, or fuel problem. Swap injector #2 into the #1 spot. If problem moves to cylinder 2, then you know that injector is bad.

Past that, it could be a # of other things.

 

[SMLEshooter]

I have a compression tester, however, I took the Jeep to a shop last week and they told me compression on Cylinder one was zero.

I brought the Jeep home, removed all six plugs. Tested cylinder one, it was zero. Tested two through six and they ranged from 160 to 170 each. Retested cylinder one at that time to make sure I hadn't installed the tester badly. It came up zero again.

At that point I was at a total loss, so took it to a Jeep repair shop yesterday. He ran a compression test on it when it got there and cylinder one was confirmed as zero compression. After he spent the next five hours tying to figure out what's wrong with it, he ran a compression test on cylinder one right before I left and it came in at 60psi. I'm going to test it again later today or tomorrow to see if it's still at 60.

Tests he conducted before I took it home at the end at the end of the day included a standard compression test on all six cylinders. A leak down test. Removed the valve cover and measured the lifters to make sure they were all lifting the valve to the correct specs. Measured the TDC of cylinder one vs TDC cylinder two. Removed the rockers on cylinder one to check for build up on the valves.

The only anomaly was the variance in TDC between the two cylinders.

I'm not new to engines. Though I may be a bit scatterbrained at times and lose track of the order of things and what other people have told me... I attribute that to getting older and overworked in general.

List of other things I've done, not in the order I did them.

Replaced the number one fuel injector. Replaced the coil pack. Replaced both upstream O2 sensors. Replaced the crank position sensor. Replaced the plugs and wires.

 

[shadowchaser59]

if you have zero compression on number one and valves are moving correctly I'd say you have a burnt valve.

 

[harrycalahan]

If #1 wont make any pressure, you're going to need to pull the head. You could further diagnose to see if its your rings or valves for sure but either way you going to be pulling the head. Could also still be your head gasket but again you're still pulling the head. As long as you've never cooked the motor, you shouldnt have a cracked block and they'll fpi the head when you take it in for a valve job. Be sure to check the flatness of the deck before taking the head in so you know you have a good block for the new head to go back on.

 

[roundhouse]

Can you pull the oil pan and look at the rods?

 

[Azznik]

I had the exact issue with my 96 Cherokee and the issue was a broken valve. I had the head replaced and everything for a little over $1k. If you need the name of the place & my contact, shoot me a pm. The guy I used is the best I know of for diagnosing weird issues.