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Old 07-23-2011, 05:37 PM
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Question 2004 F-150 5.4 engine

The engine 84k miles, developed a severe miss. I replaced the spark plugs and boots and the fuel filter. Still missed. Took it to ford dealer, the service writer said the #4 coil was bad and that the plugs needed change. I told him that I changed the plugs and boots. He said that if I did not use motorcraft plugs that my truck would never run right. I thought all after market products would do the same job. Am I right or is the guy blowing smoke? I went home and replaced the #4 coil. Road tested it and my OBDll came up with P0304 code #4 cyl miss. Has anyone out there had any similar problem? If yes what was the solution? Please Help!!!
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Old 07-23-2011, 06:34 PM
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Join Date: Jun 2010
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I believe there is a serious problem with the two piece Motorcraft plugs used with that engine. Did you have any trouble removing the old plugs?
Champion has released a new one piece plug that will not break off if difficult to remove.
If you tried swapping the plug and coil with another cylinder , do you still get the miss in #4 cylinder?
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Old 07-23-2011, 08:46 PM
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It is possible also that the bad coil allowed the new plug to become fuel fouled and still have a cylinder miss.
People are like Slinkies. Not much use, but it still makes me smile whenever I see one tumble down the stairs.
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Old 07-23-2011, 09:21 PM
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I believe #4 is the last cyl to the rear on the passenger side. There have been some reports of poor connections with the connectors that go on the coil. Make sure they are tight. Waiting to hear of your results when you swiitch the coil and spark plug with another cyl.
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Old 07-23-2011, 10:20 PM
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Default 2004 F-150 5.4 Engine

Thanks folks for the quick response to my dilemma. I had no trouble removing the old plugs but they came out very tight. I did swap the coil and plug but the miss was still there. I failed to mention that the dealer guy said that after the repairs were made they needed to flash the PCM. Obviously declined to have them do the tune up and coil replacement as I had already spent 150 bucks on plugs and boots. It would have cost me about an additional grand for them to do the work. I will recheck the coil connectors for a tight fit.

Thanks again for your help in this matter. Any other suggestions you may come up with would be greatfully appreciated. I will keep you posted if I come up with anything worth reporting.

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