F-150 rough idle issue

[waxworm09]

Two months ago i bought a 2001 F-150 with 130k. I have put 2k on the truck so far and it runs great, but is idles a bit rough. It idles at 600 rpm, is that too low? my car idles at 800. Im wondering if it might just need a tune up, plugs and wires? I bought it at a dealership, they said it had a rough idle and found 1 bad spark plug and replaced it before i bought it, maybe i should replace all plugs and wires, or what else could be the problem? Thanks

[Jeremy airjer W]

What engine?

[hardcore365]

Plug it into a computer. Free to use at most auto parts stores. My guess is a bad coil, that and a spark plug will run about 50$.

[Jeremy airjer W]

The check engine light should be on if there is a misfire large enough to cause a rough run condition. there should also be other drive ability complaints associated with the loss of cylinder performance.

[Macgyver55]

I frequently find the big vacuum line located at the rear of the intake manifold to be bad. A bit tough to get at or see but often it is the culprit.

[Fowlmouth]

Idle air control valve

[waxworm09]

It is the 5.4, the check engine light is not on. I will try hooking it up to a computer, my father in law has one i think.

[FF_205]

If the "Computer" that your father in law has doesn't have a power balance or can read live data, it wouldn't do much for you, being you said it doesn't have a check engine lite on. Like Macgyver55 said, there is a rubber elbow at the back of the intake that goes into the idle air solenoid that will get oil contaminated and collapse/rip and cause a vacuum leak, causing a rough idle, there is also one of those rubber elbows coming out of the right side(bank 1) valve cover that will do the same thing