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Rough, low idle. Why ford?

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Old Feb 5, 2015 | 09:36 PM
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Default Rough, low idle. Why ford?

Ok, so I know this is my first post and I would like to say hello to all.
Now on to my little problem, I have a 2004 fx4 screw with the 5.4. I bought it in April from a local toyota dealer. At the time, it was bone stock and running fine. Fast forward to now, over the last couple months, I have noticed more and more problems with the truck. in the past couple months, my idle has gotten progressively lower and the truck has kind of a vibration/shake/knock sittin in park or at a red light. When I acclerate steadily, it kind of surges. When I brake or (for the first time yesterday) am driving at a low speed through the neighborhood the RPM's drop to almost zero, then shoot up again.

So far, I have had the FPDM, coil packs, fuel pressure regulator, vct solenoids, spark plugs replaced, and I have cleaned my MAF and throttle body.
After replacing the coils, plugs, fuel pressure regulator, and vcts the surging has gone away. But the low idle, shaking and almost dying are still there. It is driving me absolutely bonkers.
Should I look into replacing my fuel filter in the case that it's clogged? Could that be causing my frustrations?
I know it's a 10 year old truck with 136,xxx miles on it, but this seems a little excessive.
Sorry for the long post!
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Old Feb 5, 2015 | 09:46 PM
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Originally Posted by Snoopaloop
Ok, so I know this is my first post and I would like to say hello to all.
Now on to my little problem, I have a 2004 fx4 screw with the 5.4. I bought it in April from a local toyota dealer. At the time, it was bone stock and running fine. Fast forward to now, over the last couple months, I have noticed more and more problems with the truck. in the past couple months, my idle has gotten progressively lower and the truck has kind of a vibration/shake/knock sittin in park or at a red light. When I acclerate steadily, it kind of surges. When I brake or (for the first time yesterday) am driving at a low speed through the neighborhood the RPM's drop to almost zero, then shoot up again.

So far, I have had the FPDM, coil packs, fuel pressure regulator, vct solenoids, spark plugs replaced, and I have cleaned my MAF and throttle body.
After replacing the coils, plugs, fuel pressure regulator, and vcts the surging has gone away. But the low idle, shaking and almost dying are still there. It is driving me absolutely bonkers.
Should I look into replacing my fuel filter in the case that it's clogged? Could that be causing my frustrations?
I know it's a 10 year old truck with 136,xxx miles on it, but this seems a little excessive.
Sorry for the long post!
I noticed a big difference in idle when my fuel filter was changed a couple weeks back. It had 95k miles on it then and the fuel in it was nasty. They are only about $15 for a motorcraft filter. I bought mine on Amazon.
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Old Feb 6, 2015 | 04:53 PM
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Thanks, I'll go ahead and replace the filter then. By any chance, does anyone know what the correct idle rpm should be after the truck is warmed up and driven? My tach reads high 500s ( if I can remember the correct dash increments on the panel)
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Old Feb 6, 2015 | 04:59 PM
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Pretty sure it's 6 or 700 rpms. Also, check the foam seal around the air filter tray. They tend to dry rot out and don't seal up right. You can put some adhesive-backed weatherstripping on there, it works great. I'll find you the link.
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Old Feb 6, 2015 | 05:02 PM
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Here ya go.
https://www.f150forum.com/f4/bog-dow...solved-166431/
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Old Feb 6, 2015 | 07:47 PM
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mine idles normally at around 530-540rpms when at operating temps.
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Old Feb 6, 2015 | 10:44 PM
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Possibly a IAC issue. Check your idle air control valve
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Old Feb 6, 2015 | 11:11 PM
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[QUOTE=dopewaffle;3970827]Possibly a IAC issue. Check your idle air control valve[/QUOTE

Do I have an IAC valve? I thought the 2003 and older trucks had it. Mines a 2004 new body. When I took off my throttle body to clean it, I didn't see anything resembling an IAC valve.
Thanks for the help
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Old Feb 7, 2015 | 12:24 AM
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No, you (5.4 or 4.6 3V) do not have a IAC. I second the suggestion of replacing the fuel filter. I change mine every 20K or so. You will need a special tool for the metal clips on the engine side of the filter line.
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Old Feb 7, 2015 | 12:34 AM
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Originally Posted by Summers22
No, you (5.4 or 4.6 3V) do not have a IAC. I second the suggestion of replacing the fuel filter. I change mine every 20K or so. You will need a special tool for the metal clips on the engine side of the filter line.
My bad, I'm in the wrong section ( I own a 97-03
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