Persistent misfire code P0307
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5th Wheeling
Joined: Mar 2021
Posts: 33
Likes: 3
Persistent misfire code P0307
I have a persistent misfire code P0307 (cylinder #7) on my 2017 F150 Lariat with 140,000 miles. I changed all the plugs and coil on cylinder 7. Sooner or later without any rhyme or reason the check engine lights come on again and its the same code. Can anyone suggest what else might be causing this cylinder to misfire?
Lead Driver
Joined: Dec 2016
Posts: 5,650
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From: GA
I’m not saying this would help but it might be worth a shot.
Perhaps you should take your vehicle to a shop with “dealer level” scanning equipment.
Maybe it’ll show codes that your scan tool can’t see and maybe it’ll show stored code data.
Perhaps you should take your vehicle to a shop with “dealer level” scanning equipment.
Maybe it’ll show codes that your scan tool can’t see and maybe it’ll show stored code data.
Thread Starter
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5th Wheeling
Joined: Mar 2021
Posts: 33
Likes: 3
Yep, thanks Gabar I'm also confident the software will pinpoint the fault however I'm not close to a shop, I'm about $200 away. Is there tech software on this forum or another? I have been able to get software off forums for my BMW, Volvo and Johnson, what about for Fords?
Lead Driver
Joined: Dec 2016
Posts: 5,650
Likes: 243
From: GA
Yep, thanks Gabar I'm also confident the software will pinpoint the fault however I'm not close to a shop, I'm about $200 away. Is there tech software on this forum or another? I have been able to get software off forums for my BMW, Volvo and Johnson, what about for Fords?
Lead Driver
Joined: Sep 2006
Posts: 7,907
Likes: 143
Misfire codes are based on crank shaft rotation time.
Anything that affects it will set the code when the time is too long..
Spark plug,
Coil boot,
coil,
fuel injector,
low compression,
cylinder mechanical fault,
blown head gasket.
Anything that affects it will set the code when the time is too long..
Spark plug,
Coil boot,
coil,
fuel injector,
low compression,
cylinder mechanical fault,
blown head gasket.
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5th Wheeling
Joined: Mar 2021
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I attempted to do a compression check but I don't have the correct thread adapter. The spark plug didn't seem tight when I took it out I noticed this the last time I took the plug out as well, I'll get the adapter with the correct thread and go from there. Does anyone know what the plug thread is?
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5th Wheeling
Joined: Mar 2021
Posts: 33
Likes: 3
I have 3 compression testing kits here and none of the threaded fittings work, it's almost like the threaded area on the fitting is too short and the longer threaded fittings have a different thread. Is there a special adapter for this engine, I would have thought it would be pretty standard.
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5th Wheeling
Joined: Mar 2021
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Finding the correct compression tester adapter for this engine is turning out to be frustrating, all internet searches tell me it's M14 x 1.25 14mmm long reach. I went to every parts store with no luck and then I happened upon a Snapon truck, he had one and it was $50. Get home and she still doesn't fit properly and I'm only able to get it in 3 threads and it won't tighten down to the rubber seal, I put the gauge on it anyway and I got 110psi, I'm confident that if I had the proper adapter and it sealed properly I would get a proper acceptable reading. I ordered 2 new fuel injectors from the dealer at $56 apiece, they get in 1pm and I will swap out numbers 6 & 7.
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5th Wheeling
Joined: Mar 2021
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When I picked up my new injectors at Ford I stopped over at the service department and asked the manager about the compression tester adapter for these engines and service manager told me "it's a special tool and you cannot get it in the general retail market". Is this actually true??
I installed the 2 new injectors (easier than you would think) and I ran the truck around for 20 minutes, the service light has not come on yet but it was always sporadic so I will report back in a week or two.
I installed the 2 new injectors (easier than you would think) and I ran the truck around for 20 minutes, the service light has not come on yet but it was always sporadic so I will report back in a week or two.
Lead Driver
Joined: Sep 2006
Posts: 7,907
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A better way to check misfire is with a Scanner looking at the misfire counts for each cylinder.
You will see the tendency much faster than waiting for a code and be more accurrate in solving the issue.
Sometmes all it takes is some cleaner additive in the gas to clear the issue up.
Regain has been working for me but not for any misfire issue, just smoother idle and running plus very good fuel milage numbers.
Good luck.
You will see the tendency much faster than waiting for a code and be more accurrate in solving the issue.
Sometmes all it takes is some cleaner additive in the gas to clear the issue up.
Regain has been working for me but not for any misfire issue, just smoother idle and running plus very good fuel milage numbers.
Good luck.
Lead Driver
Joined: Sep 2006
Posts: 7,907
Likes: 143
The Scanner only needs to be good enough for use after 2004 to read most of the important live data points in a later system.
I have a now discontinued unit from Sears purchused years ago that is good from 1997 to the present time for all I need to see.
Reads a lot of info you can use for most trouble shooting.
The programs are an extension of the same basic program with added functiions, so many can still be read out.
For misfire counts, you would want to look in the Test 80 area of the readouts.
I just came in from a round trip and ticked off 22.3 mpg on Regain and 93 octane fuel. 2018 5L 10 speed at an ave speed of 60 mph through the mountains up and back..
Good luck.