Hi, have a 98 F150 with the 4.6 8 cylinder. Have had problems with the truck stumbling at idle on and off for the past 2 years. The other day the truck stumbled while going down the road. It idles fine. Got it home and left it sitting. Got in the next day and it started right up and did not stumble until it got warm. Anything the excellerator is depressed is stumbles and the check engine light flashes. It only does this when it is warm, there is no pinging etc. Had the truck checked and the shop told me #7 was mis-firing. The plugs and wires have about 20k on them. No idea what the code was that the computer read. Now the shop is trying to tell me the have a TSB that says the rocker arms go bad and they think I am stupid enough to say go for it. I think the coil pack is shot. Any ideas?

 

Yeah, most likely your coil pack.

 

Check to make sure that the plug boot is snapped all the way down on the plug, also. I would try just changing that one plug before I changed coil packs, that could get expensive REALLY fast.
Good luck, and keep us posted on whatever you find out!

 

Stopped by the shop this evening. I guess they finally followed my thought process because they told me they switched the coil pack to a different bank and now that side is mis-firing. Of course, #7 is mis-firing also but that is probably due to the plug being fouled. Hopefully a new coil pack will solve the problem. Will keep everyone posted.