P0307 Misfire Cylinder #7 on 2007 5.7

lasher10 · Aug 7, 2015

The other day my check engine light came on and my truck started running rough and lacking power. When I got it home I ran error codes using my Super Paq and got DTC P0307 Misfire Cylinder #7. The fist thing I tried was replacing all the spark plugs. I can't believe what a pain in the A$$ that was. It took me almost 3 hours to change all 16 of those plugs. I have a 2007 Dodge Ram 1500 5.7 Hemi with 40,000 and this was the first plug change on the vehicle. I noticed that the 2 plugs that came from cylinder #7 were much blacker then all the other plugs. The new spark plugs made no difference. Same error code and ran the same. I swapped out the coil pack from cylinder #7 with another one of the coil packs and its still showing misfire on cylinder #7. So I've eliminated any issues with plugs and coils. Any ideas?

MADDOG · Aug 7, 2015

I assume you cleared the code when you did the plugs and coils?

If so, swap out one of the other plug wires, clear the code, then run the truck. See if the code doesn't swap over to the cylinder the wire was borrowed from.

lasher10 · Aug 8, 2015

Yes I cleared the codes. Do you mean the thin wire that plugs into the coil? That chain of wires seems cylinder specific and all tied together.

Joe.G · Aug 9, 2015

He means the spark plug wire it self, I believe you have the coil directly on 1 plug and a wire on the other plug but I am not sure on that year. If that is not the problem I would do a Leak down and a compression test on that cylinder and make sure it is ok. If that checks out fine There are a few things it could be, Fuel injector issue, Bad O2 sensors or in my case it was the Valve springs. There is more but Id start here.

MADDOG · Aug 9, 2015

I mean the plug wire.

If the code is on cylinder 7 and you swap wires (wire 7 goes to plug 3 and wire 3 goes to plug 7 for instance) and the codes are clear, if the wire is the issue you'll get a P0303 code, identifying a misfire on cylinder 3.

RonJon '06 · Aug 9, 2015

I would start by swapping fuel injectors and see if the misfire follows the #7 injector. If not then do a compression test. If there's low compression on #7 pull the valve cover and check for a broken spring as mentioned. As far as I know you can't swap the wires without cutting and splicing the wires inside the harness but you can test the voltage in the wire going to the coil.

Hellacious911 · Aug 10, 2015

Do you have any oil or residue in the #7 plug bore? I know you said two of the plugs were darker, is it carbon, burning hot, oil, etc what is it? Just saying, I had the same issue and it was a huge headache over something simple and if it's your case would be an easy fix. Clean any residue or debris within the plug bore and the one that shares it (comes from same coil pack). Grab two new plugs, install and tighten a little past recommend torque. Mine had some oil in it and wasn't sealing properly. Catch can will do wonders as well.

Again, may be far off from what your situation is, but after taking mine in and everyone and their brother couldn't figure it out, a simple aha moment made me feel really stupid. Good luck.

lasher10 · Aug 18, 2015

The Problem: Exhaust Valve Push Rod was missing from lifter and the Exhaust Valve Lifter was damaged. The spring loaded exhaust valve lifter wouldn't spring back.
The Fix: Replace Lifter Assembly. They come in a set of 4 so cylinder #7 and #5 replaced. Good as new!!!

Joe.G · Aug 19, 2015

Thank you for replying and letting us know what the issue was. I wonder what happpen to the rod, Glad you got it fixed.

RAMTRPR · Jan 29, 2017

I have replaced the coil and test new coil and injector and all are good. Still get P0307. Next is to check the plugs, but wanted to post these to see if you guys think it might be lifter assembly based on the sound. Truck has 215k on her btw

https://vimeo.com/201563491

https://vimeo.com/201563596

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RAMTRPR · Jan 30, 2017

Threw some fuel system cleaner in and the truck is running a bit smoother. Code is still gone after 50miles. I know it sometimes has to go over 250miles for it to come back so it should be back in a few days, hopefully not. I'll keep everyone posted.

Still let me know if you think it might be valve train parts.

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WilliamS · Jan 30, 2017

I have the same code on a 2014 Im chasing around.

RAMTRPR · Jan 30, 2017

WilliamS said:
I have the same code on a 2014 Im chasing around.

Good luck

at least it is a single cylinder and not general misfire

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WilliamS · Jan 30, 2017

Yeah Im going to start by moving the coil to cyl 5 and injector to cyl 3 and change the plugs see if it moved. This will narrow the misfire. If its on 3 then its the injector, on 5 its the coil, on 7 its something much too terrible that the warranty will have to fix.

RAMTRPR · Feb 7, 2017

I moved the coil on mine and no change. Moving injector next.

Side note: ran some fuel system cleaner in the truck and the code did not come back for about 400 miles or 1 full tank. Leads me to a bad or clogged injector. They are stock and have over 200k on them so they could be done

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Joe.G · Feb 8, 2017

Swap the injector and see if it follows it, Check You tube they have videos on how to clean your injector your self if you are trying to save a few bucks. I am not sure what they cost new for our trucks.

Marciel · Feb 16, 2017

Joe.G said:
He means the spark plug wire it self, I believe you have the coil directly on 1 plug and a wire on the other plug but I am not sure on that year. If that is not the problem I would do a Leak down and a compression test on that cylinder and make sure it is ok. If that checks out fine There are a few things it could be, Fuel injector issue, Bad O2 sensors or in my case it was the Valve springs. There is more but Id start here.

My 06 has a coil that accepts 2 plugs, the only wires are small Guage one coming from the ecm. I put granatelli pro street coil packs on and haven't had any issues, outrageously expensive though.

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jamie44 · Jun 14, 2018

Im having the same problem on an engine that only has 40K on it. Ive changed all plugs, wires, coil packs, crank sensor, and swapped around fuel injectors. the problem only happens in OD or 4th gear at highway speed between 1500-2000 rpm. And doesnt do it all the time, it randomly does it while driving.

LCACER · Jun 14, 2018

jamie44 said:
Im having the same problem on an engine that only has 40K on it. Ive changed all plugs, wires, coil packs, crank sensor, and swapped around fuel injectors. the problem only happens in OD or 4th gear at highway speed between 1500-2000 rpm. And doesnt do it all the time, it randomly does it while driving.

May or may not help, on my old 2010, I had a #1 Cyl misfire code. It ended up being a lifter and found out further that the rocker arm to that lifter was not moving as fluid as it should be. The dealer pretty much replaced the entire upper half of the motor trying to figure it out. Mine had a ticking noise though, that's what lead me to the lifter.

P0307 Misfire Cylinder #7 on 2007 5.7

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