Cylinder 4 misfire. Please help!

Matt0901

Matt0901

New member
I have a 2012 Jeep Wrangler with only 70k on it with a cylinder 4 misfire. I changed everything including a new cylinder head. Prior to replacing the cylinder head I was getting misfires from cylinders 2, 4, and 6. Any suggestions are much appreciated! Items replaced are catalytic converters, oxygen sensor, spark plugs, ignition coils, cam sensor, remanufactured cylinder head with rockers and valves and fuel injectors. And the correct fix will get a case of beer of their choice.
 
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I didn't see wiring checked on your list, did you check the coil plug wiring for pushed in pins, signal, resistance?

What is the code or codes?
 
jeeeep said:
I didn't see wiring checked on your list, did you check the coil plug wiring for pushed in pins, signal, resistance?

What is the code or codes?
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Only code is cylinder 4 misfire. The pins all look fine. I have not checked the resistance. I'm terrible with wiring/electrical work but I did order new pigtails for the injector and coil.
 
Matt0901 said:
Only code is cylinder 4 misfire. The pins all look fine. I have not checked the resistance. I'm terrible with wiring/electrical work but I did order new pigtails for the injector and coil.
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no other stored codes?

At this point, with everything you've already done, I'd do a compression test.

It was a much easier process when there was a central coil pack with wires.
 
Matt0901 said:
I have a 2012 Jeep Wrangler with only 70k on it with a cylinder 4 misfire. I changed everything including a new cylinder head. Prior to replacing the cylinder head I was getting misfires from cylinders 2, 4, and 6. Any suggestions are much appreciated! Items replaced are catalytic converters, oxygen sensor, spark plugs, ignition coils, cam sensor, remanufactured cylinder head with rockers and valves and fuel injectors. And the correct fix will get a case of beer of their choice.
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Wow, that’s everything I would suggest.
Good luck to you, sir.
 
JT@623 said:
Could be that coil is bad it happens do you have and old one that was working?
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This^ swap the “new” coil on cyl 4 to a different cylinder. Do 1 3 or 5 so it’s not on the same bank. Then see if it moves to that cylinder.
 
cozdude said:
This^ swap the “new” coil on cyl 4 to a different cylinder. Do 1 3 or 5 so it’s not on the same bank. Then see if it moves to that cylinder.
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I'm in my 3rd set of coils already, hoping that was my problem.... But thank you for the suggestion
 
jeeeep said:
wiring - disconnect and check the fuel injection harness main plug connection for signs of critters or corrosion in the plug
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This sounds like the direction to go.


I had a Chevy Express 1500 when I was a kid. Drove it 25K miles all over the country.

It had a random cylinder misfire the entire time. I swapped everything I could and it was intermittently better, but never cured.

I took it to three mechanics across the country and they all said it was likely an electrical issue somewhere due to all the corrosion from east coast rust. I never had the money for anyone to do a multi-day tear down on it.
 
I know you said you just had the heads, but start with a leak down check. That’s where you bring the cylinder to top dead center with a set of pressure gauges and pressurize it with regulated air pressure to see how well the cylinders are holding compression. It will tell you if you have a leak and where a leak is- valves, head, head gasket or piston rings. Until you verify the condition of the cylinder, anything else is a waste of time and money.

Do a leak down check, also known as a pressure differential check, not just a simple compression check.
 
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