Help with misfire!
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Joined: Nov 2013
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Help with misfire!
I had a 05 f350 5.4 3v come into my shop with a CEL. Did the usual it had a p0307. So I did the usual again changed plug and coil plug cam out no prob they were done 15k ago. Test drove a few times and it was fine. Few days later customer brought back with same code p0307. thought maybe I got a bad plug or coil so I moved them to #6, misfire stays on #7. When I drive it local its fine when I go to pull on to highway and really put my foot in it CEL flashes (misfire) and it pings like crazy and loses all power. Scan it back at shop and still only p0307!! Any opinions appreciated.
New User
Joined: Nov 2012
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I had to change all my coil packs and plugs at the same time for mine to quit misfiring. It just didn't work out well changing the only one that was bad. So I broke down and spent the $600 and had all the plugs and coil packs changed at the same time. Several thousand miles later it still runs like new.
Elder User
Joined: Jan 2002
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It is better (cheaper) to properly diagnose the problem rather than just start replacing parts. The trouble codes are infamous for identifying the wrong cylinder on misfires. Here is a tool that does a good job:
Here is a video that shows how to use an automotive scope to identify bad coils.
You could also have a bad injector, bad control wire, problem with cpu, etc., but most likely a bad coil, plug, or boot. Good troubleshooting starts with probability based on symptom, then process of elimination. Guessing can make you crazy and cost a lot of money.
Good luck with it and let us know what you find.
Here is a video that shows how to use an automotive scope to identify bad coils.
You could also have a bad injector, bad control wire, problem with cpu, etc., but most likely a bad coil, plug, or boot. Good troubleshooting starts with probability based on symptom, then process of elimination. Guessing can make you crazy and cost a lot of money.
Good luck with it and let us know what you find.
6th Gear
Joined: Feb 2008
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I have had three different issues with my '02 5.4 misfiring.
1. Water gets down in the spark plug hole (around the plug base) causing it to misfire. I take off the coil packs one at a time and blow out the water with the air gun. Ford Tech told me "oh, you shouldn't wash the engine because water gets down into the plug indents.
2. When I put the coil packs back on, one of the coils did not go back on the plug correctly. Took the coil pack off and reinstalled correctly. OK after that.
3. Had two bad coil packs. Bought 8 new Accell coil packs from Summit Racing. That took care of that problem.
1. Water gets down in the spark plug hole (around the plug base) causing it to misfire. I take off the coil packs one at a time and blow out the water with the air gun. Ford Tech told me "oh, you shouldn't wash the engine because water gets down into the plug indents.
2. When I put the coil packs back on, one of the coils did not go back on the plug correctly. Took the coil pack off and reinstalled correctly. OK after that.
3. Had two bad coil packs. Bought 8 new Accell coil packs from Summit Racing. That took care of that problem.
Elder User
Joined: Jan 2002
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I guess if you don't have the tools or don't know how to troubleshoot the problem, that may be a viable, though expensive, solution. I just hope that someone doesn't do that only to find out that the problem is bad control or ground wire or a bad injector causing the problem. Same symptom. A little dielectric grease on the boots does wonders for the water problem.
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6th Gear
Joined: Feb 2008
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DavidB,
I do have all the tools and I know how to troubleshoot. That is how I was able to determine exactly which coil packs were bad. I only listed the three problems I had which caused my misfire. I didn't say there could be no other causes of misfires. You made an assumption. You know what happens when you assume.
rockokloco
I do have all the tools and I know how to troubleshoot. That is how I was able to determine exactly which coil packs were bad. I only listed the three problems I had which caused my misfire. I didn't say there could be no other causes of misfires. You made an assumption. You know what happens when you assume.
rockokloco
6th Gear
Joined: Feb 2008
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Again, you are assuming. I new which two were bad. I did not need to guess. The boots dry out and shrink over time. Instead of taking all 8 out and reinstalling with DG, and replacing 2, I decided to replace all 8, with DG on them. Money was not an issue. And, I wanted all matching coil packs. I only stated some facts about my particular situation.
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