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Old 04-10-2009, 05:44 PM   #1
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Default rough idle & reduced gas mileage

I have a 2005 F150 5.4l with 70,000 miles. recently my mileage dropped to about 10 MPG around town and I have noticed that the engine idles rough. Any thoughts?
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Old 04-10-2009, 05:47 PM   #2
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How's your air filter looking. Possible time for a good tune up and maybe some injector cleaning
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Old 04-10-2009, 06:20 PM   #3
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The air filter was replaced a few hundred miles ago and I used some injector cleaner in the gas tank a few tanks ago.
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Old 04-10-2009, 08:38 PM   #4
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Sounds like time for a Tune-Up, and a good Everwear Fuel Treatment.
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Old 04-26-2009, 05:49 PM   #5
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try a can of SeaFoam. Pour a 1/3 can down your throttle body, and let sit for 5 minutes.Pour the rest of the can in your gas tank, then put your air cleaner back on, start truck and watch all the gunk & smoke come out of your exhaust. This is normal and you will notice the truck will run smoother and quieter also. I get mine from Napa($ 12Cdn-8-10Us). Good luck
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Old 05-05-2009, 06:48 PM   #6
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I poste earlier about my problem of dying at low rpm and some rough idle and I cleaned the ICV and nothing found out the Mass air flow sensors was dirty and they cleaned it and runs good now. Try this and I hope it helps
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Old 05-08-2009, 05:37 PM   #7
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Default Rough Idle 2004 4.6

Thought I would jump in. I too have been having a problem with a rough idle on my 2004 4.6 v-8. (50K miles) I took it to the dealer twice. He said there were no codes present? Here's what I did so far:

Cleaned fuel injectors
had them do a PCM update for rough Idle
Changed the PCV Valve
Hand them check the COP and Plugs
Replaced Fuel and Air Filters
Ran a tank of high test ..no ethanol
Cleaned the MAF sensor


It still idles rough while at traffic light. I can feel it in the pedals and in the dash. Mileage dropped 4 MPG.It never used to be this way.. it ran smooth as silk.

I dont understand... about to give up on it. How about a bad O2 sensor? Could the O2 sensor be going bad and not throw any codes?

I appreciate any ideas.

Last edited by Liber8tor; 05-12-2009 at 03:40 PM.
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Old 05-08-2009, 10:09 PM   #8
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Mine did that until i replaced the IAC idle air control valve
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Old 05-09-2009, 10:56 AM   #9
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Try cleaning your Mass Air Flow sensor and you can go on line and it will give you step by step instructions and what to clean it with. Mine was doing all that and we couldn't find it and the mechanic went on line and they said clean the MAS. I looked it up and they suggested cleaning it every 6 months which I think my be a little over board but what do I know I didn't even know where the MAS was.
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Old 05-12-2009, 01:25 PM   #10
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Default I cleaned MAF sensor..easy to do.. but still rough idle

Thanks Fshfndr for the good suggestion.

I don't think it is the IAC valve. I just read that the IAC can't be cleaned.. it's not a user servicable part. It has to be replaced if bad, and the symptoms don't match mine.

The most frustrating part.. is that nothing is throwing a DTC code. I'm kind of looking back towards the idea of a vacuum leak somewhere.

Also , still wondering obut the O2 sensors? I have The Flowmaster Cat-Back American Thunder System. It hasn't presented any problems so far. I wonder if it has affected the O2 sensors because its not the stock mufflers? Then again.. its not throwing any codes? The mystyery continues...

Thanks

Last edited by Liber8tor; 05-12-2009 at 03:38 PM.
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Old 05-12-2009, 01:25 PM
 
 
 
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