My 98 F-150 with a 4.6 has gotten to where sometimes (about once or twice a week) when I crank it up - you almost can't keep it running. This may keep on until you get where you are going and shut it off and let it sit a while or it may run fine in a few minutes. Sometimes it may go two weeks without doing this or it has done it three days in a row (once a day). I used Sea-foam a couple of months ago and have a fairly new K&N air filter.
Thanks in advance for any advice.
Eldon

 

have you noticed any sort of patterns (ie, is the weather a certain way when this tends to happen, etc etc)?

 

Usually it is the second time during the day that it is ran. 2-3 hours after it is shut off. It has done it in cool weather and warm weather. Hardly ever the first time in the morning.

 

most of the rough idle problems here can be solved by cleaning the IAC.

It should be a fairly easy job, and you can find several recent threads here about how to clean it, where it is, etc.

 

Thanks, I'll try it and see what happens.

 

I would also change your fuel filter. I had similar rough idle, new fuel filter, and my computer read, turned out I had a misfire on cyl # 4, changed out all the plugs. No more rough idle. Worked for me, might work for you as well.