I have an 05 f150 with the 5.4l with 113k miles on it. It normally idles perfectly, but occasionally engine speed drops about 100rpm and wavers slightly with a rough idle, but then gradually evens out to normal idle, and repeats. I haven't been able to isolate whether this happens in warm vs cool temperatures but i've been able to recreate it in Park, Neutral, And Drive. This is really the first computer controlled car I've dug into so I'm lookin for anything, don't be afraid to dumb down your answers.

My mind first went to a missfire, other threads here have also talked about clogged injectors, MAF, and IAC.

 

Have the plugs been replaced ?? clean the MAF

 

maf sensor, iac and plugs.. start with the first two

 

Clean MAF and IAC. Then diagnose from there.

 

IAC definition please? MAF, Screw, Scab I've got those all down, lol.

 

just wondering if my 05 4.6L has a IAC???

 

Intake air control I believe

Note sure about the 4.6 but the 5.4 does not have one.

 

idle air control

 

I have no reason to believe the plugs have ever been changed. I'm changing them soon, its already going to be a chore, no reason to let it get even worse. Should I do them all at once or should I do one at a time for diagnosis sake?

I know you can clean the MAF by just spraying it with MAF cleaner. Is the IAC this easy?

 

Do it all...change the plugs clean the MAF and IAC...your truck will love you..make sure you use MAF cleaner..