'05 5.4 cylinder 4 issue - Ford Truck Enthusiasts Forums

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'05 5.4 cylinder 4 issue

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Old 10-09-2018, 02:47 AM
James Tracy
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'05 5.4 cylinder 4 issue

Hello all, curious if there's anyone that have one cylinder in particular causing them grief. My '05 5.4 has 280 000km (174 000 miles) on it. The first 2/3 of that mileage was a good balance of commute/towing/sport. The last 1/3 it has been mostly short commutes and light towing. I'm on my 3rd set of plugs and coils. The previous set #4 was destroyed in less than a year. When the 3rd set was installed 7 months ago compression test showed #4 down significantly but not worrisome for what the truck does now. Under "prolonged moderate" or short hard load, #4 misfires. The plug has been pulled twice to make sure its not deteriorating. My uneducated guess is that with the compression loss in #4 it can only sustain so much pressure. Seems to be a lot better when I keep my shift points at 2500rpm or less and cruising speed at 2000rpm or less
 
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Old 10-11-2018, 11:29 AM
Rumble phish
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Have you put a scanner on it? Is it showing a check engine light or throwing any codes? You definitely have an issue in #4, and it doesn't sound like it's electrical. Have you tried swapping and known "good" COP onto the #4 plug and moving the COP on #4 to another cylinder to see if the misfire follows the COP from #4? The loss of compression in #4 you say is "significant". What is significant? What is #4 at compared to the other cylinders. I think this loss of compression is going to lead you to your issue.
 


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