I have a '01 F-150 S-Cab 5.4L with approx. 6000 miles on it. Only recently started driving most everyday, before was mostly weekends etc. Over the last month or so it has developed an intermittent rough idle. There are times when slowing to a stop that the truck almost seems like it is "lunging" feeling almost like it does with warped rotors but brakes are smooth and it obviously is coming from engine. Once you stop you can feel the vehicle shaking and hear the idle going up and down (not a great deal but enough to certainly notice...Also AC or defroster is not on. You may then drive to the next stoplight and the idle be just fine. Took it to dealership today as warranty runs out in 2 months and they said that engine performs as normal. I am pretty disappointed to say the least. Advisor said that 5.4's were notorious for a little roughness occasionally. Any past experiences or advice would be appreciated. Thanks.

 

My '98 with 5.4L with 83000mi does the same thing. I've also found that when it happens, if I slip it into neutral and blip the throttle, then it is smooth again when I drop it back into gear. New plugs and injector cleaning doesn't fix it.

Now on the suspect list: IAC valve, MAF sensor, O2 sensors, vacuum leak, etc.

Since you posted this back in March, have you found a fix yet?

 

W2,
Well the warranty actually ran out in May and the dealership pretty much stayed with their NO Check Engine Light / Problem Codes....NO PROBLEM attitude. They certainly seen how it would run well at a stoplight and then maybe in the next block begin to idle rough and shimmy etc. It seems to maybe not be quite as bad as it was or either I have just gotten used to it. Still fairly dissapointed with Ford as I had an 82 F100 with over 200K on it and a 300 6cyl engine and never had the first motor problem. The old saying "they don't make em' like they used to certainly comes into play. I will most likely be selling it soon (only 9600 miles on it and is showroom new in appearance) and going with another brand as I know too many folks having issues with the newer Fords. Don't mean that I won't have problems with something else but I am willing to try at this point.

 

Sorry to hear that you've continued to have problems. I've driven Fords for over 25 years, and am generally very happy with them. This is my third Ford truck (1974 F-100, 1992 F-150, and 1998 F-150).

I'm going to try cleaning the IAC this weekend to see if this helps. The IAC went bad in my wife's 99 Mountaineer.

I hope that you find something that serves you well.