Anyone else out there have a 2003 xlt v8 4.6L that seems to keep getting a rough idle and missing symptom after a while. I have changed plugs and a couple of the coil packs on the drivers side already. Each time I replace the back plug and coil pack, it seems to run fine for a few months, but then it comes back. Just wanted to know if I am the only one seeing this, or is this a common problem with this engine. Or maybe there is something I can do different to help it out.

Thanks
bman59

 

I have the same engine in a 2001. I had a rough idle and when I would come to a stop (after the engine was up to temp) my RPM's would deep down to below 500 and then jump back up to above 600. Seems a little different then your missing symptom that you are having. The truck always did this and I never thought anything about it. My check engine light tripped about a month ago and it was the EGR Sensor. After I replaced that my rough idle and RPM deep/jump has gone away. It was only a $35 and took all of about 15mins to change.

Not sure if this helps.