Misfire cylinder 2 - inherited Jeep

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Jun 13, 2025
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Maine
Quick backstory on the Jeep - I inherited my father’s Jeep when he passed, I’m not entirely sure what’s done to it for mods but there’s like 14,000 in receipts. It has 140,400 miles on it but the engine is stock (as far as I can tell). My wife and I took it for a ride with a full tank of new fuel (91 octane) and it threw two codes. One being the camshaft position sensor and the other stating a misfire in cylinder 2.

I put in a new OE camshaft position sensor, and cleared the code assuming that may cause the misfire, but the misfire came back with another code saying the crankshaft position sensor was faulty. I replaced that and cleared it again just for the misfire to come back. Got new plugs as the cylinder 2 plug wire was arcing (found this out at night). I replaced all the plug wires with new OE equivalent and also put new Champion spark plugs which I gapped correctly then cleared the codes. After about ten miles of driving the misfire came back in cylinder 2.

Checked all of the vacuum lines, and the wiring leading to the coil and the cam/crank sensors - they are absolutely fine, no chaffing of wires and no vacuum leaks.

The right side of the valve cover is leaking a very small amount of oil (above the exhaust manifold), and I did notice a lot of black soot around the tail of the exhaust. Scanner shows my converter as “red” but I assume that would be caused by the actual misfire in the first place.

Will be ordering a compression tester soon and can update here with the numbers for each cylinder. Just wondering if anyone has any ideas before I dig deep and tie up my garage.
 
So there were no codes, then you drove it and it tripped the light?

2004, 4 cylinder...did they have the OPDA and sync issues?

-Mac
 
Quick backstory on the Jeep - I inherited my father’s Jeep when he passed, I’m not entirely sure what’s done to it for mods but there’s like 14,000 in receipts. It has 140,400 miles on it but the engine is stock (as far as I can tell). My wife and I took it for a ride with a full tank of new fuel (91 octane) and it threw two codes. One being the camshaft position sensor and the other stating a misfire in cylinder 2.

I put in a new OE camshaft position sensor, and cleared the code assuming that may cause the misfire, but the misfire came back with another code saying the crankshaft position sensor was faulty. I replaced that and cleared it again just for the misfire to come back. Got new plugs as the cylinder 2 plug wire was arcing (found this out at night). I replaced all the plug wires with new OE equivalent and also put new Champion spark plugs which I gapped correctly then cleared the codes. After about ten miles of driving the misfire came back in cylinder 2.

Checked all of the vacuum lines, and the wiring leading to the coil and the cam/crank sensors - they are absolutely fine, no chaffing of wires and no vacuum leaks.

The right side of the valve cover is leaking a very small amount of oil (above the exhaust manifold), and I did notice a lot of black soot around the tail of the exhaust. Scanner shows my converter as “red” but I assume that would be caused by the actual misfire in the first place.

Will be ordering a compression tester soon and can update here with the numbers for each cylinder. Just wondering if anyone has any ideas before I dig deep and tie up my garage.

I just checked the vacuum with a Mityvac hand pump vacuum and it held 20lbs of vacuum without any slow leaks just to ensure I didn’t miss anything.
 
Quick backstory on the Jeep - I inherited my father’s Jeep when he passed, I’m not entirely sure what’s done to it for mods but there’s like 14,000 in receipts. It has 140,400 miles on it but the engine is stock (as far as I can tell). My wife and I took it for a ride with a full tank of new fuel (91 octane) and it threw two codes. One being the camshaft position sensor and the other stating a misfire in cylinder 2.

I put in a new OE camshaft position sensor, and cleared the code assuming that may cause the misfire, but the misfire came back with another code saying the crankshaft position sensor was faulty. I replaced that and cleared it again just for the misfire to come back. Got new plugs as the cylinder 2 plug wire was arcing (found this out at night). I replaced all the plug wires with new OE equivalent and also put new Champion spark plugs which I gapped correctly then cleared the codes. After about ten miles of driving the misfire came back in cylinder 2.

Checked all of the vacuum lines, and the wiring leading to the coil and the cam/crank sensors - they are absolutely fine, no chaffing of wires and no vacuum leaks.

The right side of the valve cover is leaking a very small amount of oil (above the exhaust manifold), and I did notice a lot of black soot around the tail of the exhaust. Scanner shows my converter as “red” but I assume that would be caused by the actual misfire in the first place.

Will be ordering a compression tester soon and can update here with the numbers for each cylinder. Just wondering if anyone has any ideas before I dig deep and tie up my garage.

I just checked the vacuum with a Mityvac hand pump vacuum and it held 20psi without any slow leaks just to ensure I didn’t miss anything.
So there were no codes, then you drove it and it tripped the light?

2004, 4 cylinder...did they have the OPDA and sync issues?

-Mac

No codes for the first couple hours, no dash lights, then it started idling rough and surging with a CEL, so I plugged my scanner in and got a P0302. That’s what started this whole adventure. I’m not entirely sure if the 2.4 has issues with heat soak, but I’ll do some research. I thought the OPDA was usually a 4.0 issue, but may be wrong.
 
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Yeah the 2.4L is a very different DOHC motor from the 4.0L and 2.5L that lived through most of the YJ/TJ era and unfortunately isn't as well known in the Wrangler world.
 
Did a compression test and a wet compression test today with the help of my wife.

Dry test:
Cylinder 1 - 150
Cylinder 2 - 40
Cylinder 3 - 146
Cylinder 4 - 146

Wet test:
Cylinder 1 - 153
Cylinder 2 - 49
Cylinder 3 - 146
Cylinder 4 - 149


I think she is toast boys and girls