Random Misfire, No Codes

Screwdriver to the injector and one end to your ear and listen for clicking.

My old ones looked like shit but my guess is they weren't bad at all.

-Mac

So check for the clicking. I think my buddy felt them with his fingers, but I can check again.

Jerry is waiting for me to do a compression test, which I can do but I wanted to try a few easy things.
 
I'll figure out how to use this thing and give it a shot.

Have you pulled a fuel sample? Put it in a clean jar let it sit for a bit.
Are you sure it’s a misfire and not an engine vibration? Broken flex plate, slipped balancer, high oil level. If it’s a misfire put a vacuum gauge on it to see what it’s doing. Compression and leakdown test also to verify engine condition.
 
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Have you pulled a fuel sample? Put it in a clean jar let it sit for a bit.
Are you sure it’s a misfire and not an engine vibration? Broken flex plate, slipped balancer, high oil level. If it’s a misfire put a vacuum gauge on it to see what it’s doing. Compression and leakdown test also to verify engine condition.

I haven't done any of these things, I don't know anything about them, actually, but you have me curious.

Two of my buddies are gear heads so I asked them and they said it was a miss. Personally I don't know what a miss sounds like, never had a vehicle do it before. I wish I could describe the sound better or capture it on a microphone. It's a almost a minute hesitation, pause, or low cough sound that makes the Jeep shake when it happens. It's only consistent in that it happens. It may be one every several seconds, then a few in quick succession, then once every few seconds, then stops for several seconds.

I looked up how to do the compression test, so I'll be doing that today or tomorrow (my lady's car is having brake problems so I'm working on both today).

How can I tell if it's any of these others?
 
Oh, I have a vacuum tester hand pump that I used to find a vacuum leak, would this work? Am I just hooking this up while the engine is running? There's that extra port on the intake that just has a cap over it.
 
Oh, I have a vacuum tester hand pump that I used to find a vacuum leak, would this work? Am I just hooking this up while the engine is running? There's that extra port on the intake that just has a cap over it.
Yes hook it up check it while running it should be 18” and steady
 
Yes hook it up check it while running it should be 18” and steady

Cool idea! I'm looking at the relay box at the moment, found that the previous owner spliced a new section in the wire feeding the fuse pump relay. Not sure if this is a factor or not, but once I button it back up I'll try the vacuum tester.
 
Could this be a problem with the distributor? My second set of hands won't be here until this weekend, so I'm going to do the compression/leak down tests then, so I'm curious what I can test in the meantime.
 
My mechanic discovered my ignition coil was broken along its length. Replaced it and cleaned up the contact, the missfire isn't gone but it's better.

Compression test showed all six within 10%.

It seems like the miss isn't happening when it first starts now, it starts to warm up sounding fine. Then it starts. I had trouble starting it on and off the past few days, seems to start missing a lot sooner when it struggles to start. It's almost like the battery is low, but I checked and it's holding high 12vs.

Not sure what to do at this point.