I have a 1998 F-150 with 181,000 on it. The problem that I am having is that when I am stopped sometimes it idles smooth when in high idle it then seems to kick into a low idle and the engine becomes very rough as if it is going to stall. If I goose it when I am pulling out it will run fine but if I pull a slow start when it is rumbling it seems to bog for a short span. I have already replaced the idle sensor on it with no luck. Any other suggestions? Also when I turn off the truck it seems to whistle up near the firewall for about 10 secs.

 

Could possibly be a vacuum leak. I'd check the lines near the fire wall if that's where the sound is coming from.

 

Thanks Bullitt94 have to give that a try JT