Empire

EDIT - Cliff Notes - Misfire issues
- engine stumbling a lot
- obvious misfire - did the "usual" stuff to try to fix it, new plugs, new coils, still missing
- according to the codes, it is a coil issue
- research indicates that it is a "multi-fire" spark issue. not getting secondary spark on one or more cylinders, as the misfire goes away at 2k rpms and above.
- currently, cleared the codes, waiting to see what comes back
- code of major concern - P0351 ignition coil A primary/secondary circuit malfunction. What does this mean in English?

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I'm in over my head.
I need help from someone more knowledgeable about these trucks/this engine than just my general knowledge.


It is a 2003 F150 Supercrew. 4.6 liter engine.

It has a misfire from idle to 1,500 rpms.

Symptoms.
-At idle, it shudders. It isn't really a consistent miss, but it is there every couple of seconds. This happens both, in neutral, and in gear.
-revving in neutral, you can hear the misfire consistently until about 1,500 rpms, then smooths out.
-In gear, accelerating like normal, it misses enough to have a dramatic effect on power, until about 1,500 rpms, then it "lets go" and pulls like it should.
-From a stop, if you stand on the throttle, it will accelerate, but there is a noticeable difference in power once you hit the 1,500 rpm mark.
-I say 1,500, it isn't a hard cut right there, but between 1,500 and 2,000, it starts to behave. Once you hit 2 grand, the symptoms are gone.
-When cruising at speed, (45+) the transmission drops into overdrive, if you press the throttle just a little bit more, it will shudder very badly. Once it starts shuddering, you have to all but kick the throttle to get it to stop tripping over itself and shift out of overdrive. There is no light acceleration in overdrive.
-Going up a hill, the shudder is really bad, unless you hit the throttle enough to downshift and get the rpm's up.



So far,
- Cleaned the MAF sensor, got some crud off of it - no change in misfire
-I've replaced the spark plugs and coils thinking it was a bad coil. - no change.
-maybe I got bad coils - pulled them out, wrapped the boots up in electrical tape, one at a time, tested for spark, each one had a nice solid spark. reassembled. - no change.
- moved the coils around hoping to identify a bad one - no change.
I've not been able to discern it being a single cylinder causing the issue.
-replaced the IACV. the old one was going bad, it has been "humming" for a while now. got the new one in, got it adjusted and all that - it seems to run a bit better, but the misfire is still there.
- sprayed carb cleaner, starter fluid, electrical contact cleaner all over the engine bay trying to find a vacuum leak, couldn't find anything.


beyond soaking it in diesel and setting it on fire, I don't know what else to do to it.