Saturday I leave the house headed for the coast 2.5 hour drive. It’ s a colder day and raining. Truck runs fine no issues which is strange because it has been in need of a good tune up for a few months now. It has been running horrible but you could tell a slight hesitation or a rough idle. Truck sites overnight in a hotel parking lot. Next day it is slightly warmer headed back home and the truck is running rough sound bad big hesitation when accelerating. Get it home does the same yesterday morning and afternoon.

I take the truck to advanced auto parts they scan it returns a misfire on cylinder 4. OK I figure I have burned another coil pack. I was meeting friend so I left there when straight to the restaurant. Temp dropped about 7 degrees from 62 to 55 in the 3 hours we were in the restaurant. Truck ran fine going home and this morning coming to work. Other than the obvious of needing a tune up (got around 110,000 miles on this set of plugs) why is it doing this? Does the 6 degrees in temp really make that much of a difference?

 

Give it a good tune up, starting with motorcraft plugs.

 

I'm thinking coincidence. When my first died, it ran crap sometimes, other times fine. The second time, same cylinder (3), it ran crap all the time after it warmed up a minute or 2.

 

you got a bad coil or atleast the connection is bad.. Over time the dielectric grease used to protect from water degrades and you get a nice rainstorm and missfire.. If you havent ever changed your plugs nows a good time.. I'd look at a new set of coils to..

 

Thanks
Carried the truck in yesterday. Decided it wasn't worth $125 for me to change plugs after work. Getting plugs changed and coil boots and springs replaced. If there is a bad coil as suspected all of will be $240 if not $200.