Yep, I'm with cooperman. Coil packs age and this might be a sign that yours is getting tired. If it starts to recreate the same symptoms again suspect its on its way out' you might also have loss of power from an inadequate burn if the spark is too small. Incidentally ford revised their iridium plug gaps to 1.2mm which resolved the problem they had with coil packs failing, their original setting was 2.5mm which caused plug failure and then coil pack failure as the gap became so large that the coil was under immense strain, coupled with heat they failed on a regular basis! Hope that helps.
The iridium plugs I fitted 20k miles ago were gapped to 45 thou, which is standard spec, and they had opened up. I brought them down to around 35 thou, exactly as Peter says the recommended gap for tuned engines.
I'm not worried at all by the condition of my coil packs, they are GM not Ford units and have no history of failure. I'm more concerned by battery voltage, although it's a newish battery I'm not seeing the volts I would like, but the engine spins quite happily and now starts exactly on the 2 seconds cranking that the ECU is set to before it fires.
I'm happy to conclude that the issue was caused simply by the plug gaps wearing a bit wider than the engine liked. I downloaded some run logs from the ECU and there is no data at all that's remotely out of appropriate ranges so I don't think there's any deeper issues of concern.
