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2004 4.6 dropping cylinders

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Old 10-11-2017, 12:56 AM   #1
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Question 2004 4.6 dropping cylinders

Iíve got a 2004 f150 4.6, started missing so I changed plugs and coils, ran good for about a week then started acting up, some times you start it up and it idles fine and sometimes it idles rough, and when you drive it it runs good as long as you donít put the motor under any kind of a load, the more of a load the motor is under the worse it misses, as you start letting off the gas peddle you can feel the miss leaving and feel cylinders coming back,when you floor it down into passing gear itís like itís down to 3-4 cylinders and will barely pull itís self, I took it to the shop and computer showed misfire on cylinders and o2 sensors so I changed the 02 sensors but didnít help.

any ideas appericated guys
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Old 10-11-2017, 05:34 AM   #2
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Search FPDM on this site.

It's a module located above the spare tire which has a tendency to rot out. FPDM goes, or starts going, fuel supply to the motor gets screwed up.
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Old 10-12-2017, 07:58 PM   #3
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Well I put a fuel pump drive module on today and still same thing, also changed plugs again, and new fuel filter. Any more ideas what it could be
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Old 10-13-2017, 09:56 AM   #4
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Clogged cats
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Old 10-13-2017, 12:54 PM   #5
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Just to rebound on what 650 said, drive the truck for a bit...then go underneath and look at the cats. If one is glowing red, it's clogged.
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