I have an 04 Lariat supercrew 5.4 / 2wd. It idles roughly whether in gear or in park. It's not a constant misfire. It's just a bump every couple of seconds while idling. If I leave it in park and raise the rpm to 2000 or so and hold it there, it will run smooth, but every couple of seconds it will make a quick misfire. If I put the truck in drive and raise the rpm's while holding the brake, it will not misfire. I do not notice any misfire while driving or accelerating. No check engine light and no loss of power. The truck has 72,000 miles.

 

You have a missfire probably caused by a bad coil/ Get your codes read this misscode is probably stored in there or just wait a few more days and your CEL will come on. If you get the code you can swap the affected cylinders coil with a known good one see if the miss moves. Might just be time to get some new plugs and e-bay dg-511 coils and tune it up..

 

agree..sounds like its time for plugs/coil change

how longs the fuel filter been on there..may wanna change that and run some seafoam/techron through the gas tank

 

just noticed its a 2004..better go to the dealer for the plug change