I've been experiencing a rough idling 2003 Ford F-150 4.6. I've changed the fuel filter and cleaned the MAF and neither has made a difference.

I've been reading posts and think I might have a vacuum leak (and let me say I'm not looking forward to finding it). I've been searching for a vacuum hose diagram, but can't find one for this vehicle.

Can anyone direct me a good one or give me some ideas as to what else to take a look at, please?

Thank you all in advance,

 

Spark plugs or cop's or boots could also cause rough idle. How long since it was tuned up?

 

Remove the black plastic filter contraption going to the air filter and see if the throttle body is dirty. Mine had black gunk all inside ..... I took a can of carb cleaner and a rag and got all out and the idle straightened up.

 

Mine was at a rough idle and it turned out to be a fuel injector. My CEL was on though.

 

I am with Greg B........if that was my truck this is what i would do. I would bring the mantannce up to snuff ie. tuneup. plugs, wires/cops, pcv, clean iacv, air filter, clean TB, etc. as you do the tuneup look for vacuum leaks. I would also check for codes even if the cel is off. in my experieancing on these forums and in the real world the majority of problems are are maintenance related.. Throw a new gatorback belt on it and at a minum maybe a lower radiator hose and clean the battery terminals......