Storm Trooper

hi i have a 2009 f-150 4x4 stx with the 4.6 v8 and it has a kinda rough idle at times.some times it idles perfect i tried serching but came up empty. my truck has 35,000 miles on it i wes wondering if anybody has an idea?i was thinking it might be the fuel filter but my truck dident have a book so i am not sure where the fuel filter is located thanks.

Rayman21186

It's not the fuel filter. The filters in our trucks are not serviceable. They are supposedly "lifetime" fuel filters.

travlnman

Please see my recent thread about rough idle with the AC on...mine is just with AC on. Otherwise, she is smooth as butter, but AC on and in drive, the RPM drops too low (500 rpm or less) and gets real rough. The servo throttle body should bump up the rpm to comp for the load from the AC. You may want to see if yours is under the same conditions. I have no solution yet...but when I do, I will chime in for sure .

travlnman

Also, I think we have pretty much the same truck, mine is 2010 STX, just not 4wd...it's a two valve 4.6.

Storm Trooper

ok thaks for the replys well i will rule out the fuel filter. and i will check the idle when i run the a/c on .

Storm Trooper

the a/c made no difference in the idle. my truck idled great today.