Just replaced my coil for the second time due to P0300 random misfire. Bought my 06 longbed 2.3L manual Ranger with 49k miles. Seemed to have a slight stutter when cruising. Replaced plugs, wires, fuel filter and seemed to still be there. No check engine light but the scanner showed pending code P0300 random misfire. So last but not least I replaced the coil. Cured and seemed to run so much better. Kind of surprised me being the truck probably had very low 50k miles at the time. Here at 72k it starts again and throws the code as the truck starts to run rougher pretty quick. Knowing the plugs and wires were not that old, checked just the same, I stepped out on a limb and replaced the coil again, bought a nicer Delphi coil this time. Viola, cured again. Seems to be a pretty short life span on coils for some reason or maybe I just have bad luck with them. I don't remember the brand last time. Anyways, happy the little Ranger is purring very nicely again. Wonder if I buy a third coil and leave it in the box behind the seat if it will run great for a longer period of time??? LOL!!!

 

Well "new" no longer means "it works", new now means "never tested"

I guess you will have to wait and see if the old "new" coil was just poorly made.

Ford did have a batch of bad coil packs used in the 3.0l's in the early 2000's, so it can happen.

Spark plugs matter as well, to coil life, Motorcraft or Autolite only, and double platinum, Ford Waste Spark system will eat other brands and single platinum won't last.

 

I had this happen too. Replaced the plugs, then the wires, then the coil, finally took it to the stealership after none if that fixed it. $300 and a day off work later, it turned out my brand new autozone wires weren't "high quality enough" and just switching to motorcraft brand ones fixed it. I know higher resistance in an ignition system can put other components out of order after awhile, so it might be worth going back to name brand stuff.

 

You both may have a point. Even though the truck seemed to run great after the coil installation I wondered if some component I had installed could have lead to it's early grave. Being preemptive I replaced the NGK Iridium plugs with Autolite even though they only had about 20K on them and looked okay. They were the IX which I believe are single plated, I think. I also purchased new Taylor 8.2 wires to replace the brand I have. Don't remember who made the other replacements but maybe they were not up to par. I was getting some funky readings with an ohm meter, like 400 plus. The Taylor wires ran low 40's for shortest to low 50's for the longest wire. So maybe the wires had something to do with it.