Rough Idle

[Craigums]

2004 F-150 idles rough, and often kills during idle. It start right back up however and I have not noticed any other issues. Is there any basic things I should be checking?

Thanks

[Jeremy airjer W]

Happens when cold or hot or all the time?

Check engine light on? (Silly question, its a ford its always on.... )

5.4 liter?

[Craigums]

Yes 5.4L , Check engine light is on (code spits out something about fuel pressure and to check the gas cap). I haven't really noticed it more when it's hot or cold. Idles rough about 80% of the time. Every once in a while it'll idle really nice

[Jeremy airjer W]

I think I would check the codes again. My first thought is since its winter vacuum leaks are more common. If you see a p0171 or P0174 than I would for sure suspect a vacuum leak, plenum gaskets are fairly common.

The other possibility is a dirty MAF sensor.

[Craigums]

K, i'll check em again

[CAMAN]

Do these trucks have a replaceable fuel filter? I'd check that.

[Jeremy airjer W]

If the filter where plugged that bad it would have a noticeable performance issue. I have one filter cause a performance issue and that was 12+ years ago.

[fishnowworknever]

Welcome to the club man. My 2005 does the same thing. Do you have a K&N filter or other aftermarket oiled filter? That'll make it happen more often. Remove the throttle body, clean it with a good TB cleaner ( no need to saturate it, and don't scratch the plate).

[JOHNBIGDOG]

Does the 04 have a fuel pump driver module? I'm feeling a little to lazy at the moment to look it up. If it has one it is located above the spare tire, on the left/driver side of the truck. The aluminum housing breaks exposing the circutry inside and causes a similar complaint. Or a C.N.S. ( crank no start)

[Scott K]

The new style 04 has one(non Heritage), and it isnt above the spare tire until 05. The 04 has it mounted on the LR frame rail, and it is actually more common to go bad then the later ones, that are above the spare tire.

[Craigums]

My first thought is since its winter vacuum leaks are more common. If you see a p0171 or P0174 than I would for sure suspect a vacuum leak.

DING DING DING!

It turned out to be a vaccuum hose leak on the backside of the intake manifold