Just had the same thing last week with my 2002 F150 5.4L. A code scanner wouldn't tell anything because the Service Engine Soon light wasn't on. If your light comes on go by your local Autozone, etc. They'll check the code for free. When it finally came on the code said Cylinder 3 Misfire. As you might know these engine use a coil on top of each sparkplug. That's what I had to replace. It was about $49 at the parts store. Always replace the plug too. I had 160,000 miles on the original plugs. The plug gap had widened from about.054 to about.090. I'm guessing over time it burnt the coil out having to supply enough voltage/current to jump a larger gap. Ran great right after replacing the coil/plug. Be ready to replace all the coils and plugs. I just had another one go out 2 days ago and I'm in the process of replacing all 8. Found a guy on eBay that sells a set of 8 coils for about $85. If you know a good mechanic pay him $100 to replace them after you buy them. The passenger side isn't so bad (except #4) but the the drivers side is a royal pain. You'll have to lift the fuel injector rail, disconnect some vacuum lines, and remove the power steering fluid reservor top bracket to get access. Good luck. Hope this helped.
Saturday, August 30th, 2008 AT 2:27 PM