P0307 #7 misfire

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megan4221977

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Hey… ok #7 misfire… I bought truck 201k on it, ran smooth no noises, was told it was maintained… well noticed when driving on interstate, when stomping on gas to get up and go it would buck and engine light would flash… changed filter and fluid in transmission, seemed ok… did it again, happened to have computer tester and plugged in while driving and read random misfire, so changed all the spark plugs… #7 misfire, so changed all the coils packs, #7 misfire, changed fuel injectors… you got it #7 misfire still!!! Just took off the valve cover as was told could be rocker follower, they seem good very tiny to no wiggle at all!! Even checked spark at #7 and was good… know I’m stumped!! Not losing any fluid. (Coolant or oil) only this code shows, clear it runs great till you have to give a little gas to maintain speed up hill or something… then struggles, jerks, sputters, etc… check engine light flashes… clear code while driving (3xs in a row) and drives fine again. Also the spark plugs looked original!! Replaced with OEM… even did the dioeletric grease stuff on coils… any ideas/help… no engine noise, runs quiet since I got it.
 

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Goofy173

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Since no answers yet, I will just throw out it possibly being the injector harness. Also check compression.

Really seems time to think out of the box.

One thing also sticks in the back of my mind is very, very unlikely, coil 7 bad again? What would be the coincidence? I've had a brand new coil be bad just last year, but that you replaced all, and a bad one just happens to be #7 again? Not likely.

If it were mine at this point, I have a really great mechanic I would have look at it. Mine takes 2 weeks to get into but he's always found my head-scratchers. Maybe you have one of those?Mines only $75/hr where most are $90 here. Not that much considering how much time and money you've already spent.

Good luck. You need it with this.
 
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megan4221977

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Yeah I was doing compression test today! Been researching everything!! Someone said to noid light the injector. Friend is a mechanic.
 
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megan4221977

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I actually had to change out the fuel pump like 5 months ago! So everything is new there… it didn’t start till after I did spark plug change… waiting to do compression test as none of the fittings fit… had to order special one for ford!
 

Trainmaster

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You can try switching injectors between cylinders and see if the miss follows, but I believe your problem is with ignition. Triple check your ignition system. Look carefully at the connector to the coil and the leads, as a compression problem would have to be a bad one to show as a miss with a flashing engine light. That signifies the failure of the firing of the plug or breakdown of the spark.
 
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megan4221977

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Ok will switch around, cause after new coils I plugged in spark tester and was good flashing bright and quickly!!! Spark plug shows sign of firing! You know the tiny bit of discolor and little bit of soot looking… but still new… lol
 

Dennis_H

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When I replaced plugs etc. I started getting an issue. Went through the coils, etc also. Turned out to be a new plug that was bad. Didn't fire all the time for some reason, but replacing that one again fixed the rough running.
 
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