Cylinder 7 misfire

Rubelus · Sep 10, 2026

Hey guys, looking for some help with a persistent cylinder 7 misfire on my 2012 Ram 1500 4.7L.
It has a P0307 and misses mostly at idle. Once I bring the RPMs above about 1,500, the misfire basically goes away.
So far I’ve replaced:All 8 fuel injectors, all 16 spark plugs and plug wires, cylinder 7 coil, both cylinder 7 lash adjusters/lifters, cylinder 7 rocker arms
Cylinder 7 had about 150 psi dry compression; cylinder 1 had 175 psi. A wet compression test brought cylinder 7 up to about 175 psi. Spraying carb cleaner around the cylinder 7 intake-manifold area made no difference.
When I removed the old #7 rocker, I found the roller badly damaged/scored (photo attached). After replacing it, the misfire got noticeably better, but it is still present.
Does this sound more like a damaged cam lobe, a valve/seat issue, or possibly ring sealing because the wet compression test came up? What should I inspect next before I pull the head?

Thanks.

Terry O · Sep 10, 2026

These engines all have problems with oil pressure number one no oil it's up to the hydraulic lifters if the roller, so idling isn't a good idea no pressure you probably have a bad cam.

Terry O · Sep 10, 2026

That gets up to the lifters don't worry I'll get there not enough anyway.

Terry O · Sep 10, 2026

Terry O said:
That gets up to the lifters

Burla · Sep 10, 2026

Fuel PSI at rear of engine?

Mandride · Oct 9, 2026

I have the same misfire on Cylinder 7, Dealership has swapped coil and plugs to different cylinders, and the issue didn't follow it. They are now going to swap the injector and see what happens. I will keep this thread active with results. There is a good possibility the MDS lifter is bad and possibly cam. Symptoms are that at idle and light load i get bad miss fire with check Engine light coming on with misfire code. if driving it would start to flash. Luckly i was close to dealership and dropped it off with the dealership, other lucky thing is I have the Lifetime MAxCare plan if it is the MDS issue.

Mandride · Oct 11, 2026

Well mine just turned out to be a clogged injector - cleaned fuel system and runs great.

spoolinlust · Oct 17, 2026

Rubelus said:
Hey guys, looking for some help with a persistent cylinder 7 misfire on my 2012 Ram 1500 4.7L.
It has a P0307 and misses mostly at idle. Once I bring the RPMs above about 1,500, the misfire basically goes away.
So far I’ve replaced:All 8 fuel injectors, all 16 spark plugs and plug wires, cylinder 7 coil, both cylinder 7 lash adjusters/lifters, cylinder 7 rocker arms
Cylinder 7 had about 150 psi dry compression; cylinder 1 had 175 psi. A wet compression test brought cylinder 7 up to about 175 psi. Spraying carb cleaner around the cylinder 7 intake-manifold area made no difference.
When I removed the old #7 rocker, I found the roller badly damaged/scored (photo attached). After replacing it, the misfire got noticeably better, but it is still present.
Does this sound more like a damaged cam lobe, a valve/seat issue, or possibly ring sealing because the wet compression test came up? What should I inspect next before I pull the head?

Thanks.

Did you check the push rod? Is it me or does the rocker look pitted as if it sat for a while? Does the roller portion move freely? If you have the valve covers off sometimes you can get lucky and measure the valve open/closed of the bad cylinder and compare it to 2 or more others may show an indication if the cam and or lifter is trashed. @Wild one just posted a video from youtube showing how they fail and makes me think that it may be measurable to make a better informed decision on weather to pull the cam out. Also, any metal/"glitter" in the oil?
For wet compression we would always use a little bit of clean engine oil.

Wild one · Oct 17, 2026

spoolinlust said:
Did you check the push rod? Is it me or does the rocker look pitted as if it sat for a while? Does the roller portion move freely? If you have the valve covers off sometimes you can get lucky and measure the valve open/closed of the bad cylinder and compare it to 2 or more others may show an indication if the cam and or lifter is trashed. @Wild one just posted a video from youtube showing how they fail and makes me think that it may be measurable to make a better informed decision on weather to pull the cam out. Also, any metal/"glitter" in the oil?
For wet compression we would always use a little bit of clean engine oil.

He's got the old 4.7,totally differant engine from the 5.7,it's an overhead cam engine

spoolinlust · Oct 17, 2026

Wild one said:
He's got the old 4.7,totally differant engine from the 5.7,it's an overhead cam engine

Well I learned something new today, thank you!

spoolinlust · Oct 17, 2026

Obviously I don't have any experience with the 4.7, I was under the impression it was just a smaller displacement version of the 5.9. my bad

Wild one · Oct 17, 2026

spoolinlust said:
Well I learned something new today, thank you!

They quit putting the 4.7's in the trucks after 2013.
It's a completely differant engine as it's an overhead cam V8
They weren't a bad engine,just a bit small for a full size truck.They made decent power once you got them above 3500 rpm,but under that they were pretty lame.
If they'd of put the 8 speed behind them,they would of been alot better,as they needed all the gearing help you could give them

pacofortacos · Oct 18, 2026

Rubelus said:
Hey guys, looking for some help with a persistent cylinder 7 misfire on my 2012 Ram 1500 4.7L.
It has a P0307 and misses mostly at idle. Once I bring the RPMs above about 1,500, the misfire basically goes away.
So far I’ve replaced:All 8 fuel injectors, all 16 spark plugs and plug wires, cylinder 7 coil, both cylinder 7 lash adjusters/lifters, cylinder 7 rocker arms
Cylinder 7 had about 150 psi dry compression; cylinder 1 had 175 psi. A wet compression test brought cylinder 7 up to about 175 psi. Spraying carb cleaner around the cylinder 7 intake-manifold area made no difference.
When I removed the old #7 rocker, I found the roller badly damaged/scored (photo attached). After replacing it, the misfire got noticeably better, but it is still present.
Does this sound more like a damaged cam lobe, a valve/seat issue, or possibly ring sealing because the wet compression test came up? What should I inspect next before I pull the head?

Thanks.

Opps, just saw that this is month old LOL

You can tell what's losing pressure by -
1 Put piston at BDC (you can try TDC but if it's not exactly at TDC the air might push the piston down)
2 remove both rockers
3 using your compression hose, put about 5-10 psi into the cylinder (might need a bit more)
IF you hear/feel air coming out of the crankcase area - it's rings
IF you hear/feel air coming out of the exhaust - it's the exhaust valve/seat, etc.
IF you hear/feel air coming out of an open throttle body - it's intake valve/seat, etc.

It depend on how "wet" you made it when you did that test, but the above test will tell you what is leaking.

spoolinlust · Oct 22, 2026

Wild one said:
He's got the old 4.7,totally differant engine from the 5.7,it's an overhead cam engine

Copy that, ohc engines a higher RPM setups. Makes no sense unless it's geared properly or forced induction. I ran and still run little Honda civics and had a supra and integra back in the day. Rev the **** out of em and they love it.

In any event, hopefully OP gets his rig up and running.

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Cylinder 7 misfire

Rubelus

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