2009 F150 Rough Idle in Drive Only

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I've got a 2009 F150 with the 5.4 an around 91k.

In the last couple months, I have noticed a rough idle sometimes but only in drive. It only happens when I'm off the gas completely and stopped I drive. It is most noticeable in drive throughout and at stop lights. It coincides with an RPM drop as well. No check engine light.

Anyone have experience with a similar problem?

Thoughts? Coil packs? MAF?
 
I'd check for a blown coil.

Each time I blew a coil on a 5.4, it would idle fine, but with any sort of load, it would misfire. Higher RPMs (above 3000), it was also fine.

Didn't set any sort of code.
 
Could be the cannister vent valve not closing completely allowing an air leak. It only takes a small amount of air bypassing the MAF to cause a lean idle.
 
Is your AC on in any way, meaning AC, Max AC, defrost ? Mine does the same, has for a while. Have found no solution, just been living with it. Replaced MAF, cleaned throttle body, replaced PCV, cleared all codes on computer, etc, etc. Mine is only with the AC on...it is noticeably bad, yet the Ford techs say they can't notice it...figures.
 
while I've not heard of this on fords, some of the GM guys, if they are really picky, have noticed this in some of the 5.7s in the mid-2000's. they had a run of cams that weren't heat treated properly and might wear just a touch on some of the lobes, and the only real symptom was a slight, very slight, hiccup during idle.

I'd never heard of it until a wrenching buddy experienced it himself. new cam and done.

I've never heard of such with ford but I'm not around them all the time to know.

I've had a stretched t-belt do that and much more on an older subaru.
 
Not sure about the OP, but mine worked beautifully until about 75or 80K (140k now). When I change the plugs, they have no color...too lean for my taste, and most recently, have been getting a CEL (forget the #) for lean condition and says upstream O2 sensor on left side. I would bet a cheap lunch that they all have the same source...if I could find it
smile.gif
 
The rough running is noticeable to me and does seem to happen mainly when warm with the AC on.

I have run a couple cans of techron and used shell gas for some time.

Reading about plug issues I'm betting that's it. It will be hard to diagnose why plug until I get a cel. If all else fails I could grab a new set of coils but that would be pricey.
 
Try it with AC off for extended drive, about 30 mins or more, and see if you have the same issue at idle at red lights and such. I actually cleaned out my canister purge valve this afternoon and will see if there is any difference tomorrow...will post the results soon.
 
Well...for those interested, no change after cleaning the canister purge valve and clearing codes...still rough idle with AC on...CEL came back rather quickly, the search continues.
 
My wife's 02 Lincoln with the 4.6 did this for the longest time, I ran so many fuel cleaners thru it. Changed the idle valve, checked the vacuum lines. I finally just gave up. It drove me crazy. Finally a check engine light came on, bad coil pack. It even told me which one. I replaced it and it was fine. wait for the light, check it. Her car did this for aprox. 6 months before the light came on. Aggravating.
 
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