5.4 misfire fixed
I've been looking at this board for a long time, but wanted to sign in and say thanks for helping me fix a problem recently. I have a 1999 f-150 with the triton 5.4 liter and it has had a mild stumble for a long time, over the last two weeks it got a really bad misfire that shook the whole truck when driving under partial load (never noticable at full throttle or rolling along at idle). It was so bad it felt like the truck was going to shake itself to pieces when it happened.
It was intermittent, so it was tough to track down. I spent a bunch of time looking through old messages here and got some ideas.
I finally got a check engine light and was able to read the codes - number 4 cylinder was misfiring. I moved the coil pack to a different cylinder (number 1) and the misfire followed it. So I replaced the coil-on-plug and everything is runnign great. It was about $50 and it feels like a whole new truck. I think it was not working right for a long time - it felt like I gained another 30 hp once I replaced it! And the rough idle I used to get sometimes went away too.
By the way, the guy at the parts counter said that the coils have been superceeded like eleven times. Supposedly the new ones are better. He said the early ones were hit or miss with lot of failures.
Needless to say, I'm pretty happy that my truck is running right again. Thanks for the great info from this board!