...Misfire detected on cylinder #5

That's the code my Aerostar is now throwing. A little while back it started behaving like it was misfiring at idle - shaking and running unevenly. It's harder to tell at speed, but it continues to run unevenly there as well.

It finally threw the code a little while ago, so I plugged in the reader and found it reporting P0305. I replaced the plugs and wires about 6 months ago, so my first thought was that one (on #5) had popped off either the plug or the coil pack. I dug into it last weekend with the van on the lift. I checked the wire connections on both ends - no sign of being unplugged. I pulled the coil end and verified that it ran the same with/without the wire plugged in. I also verified that there appears to be a healthy spark jumping the gap if it was held close.

I pulled the plug on #5, hoping it would prove to be fouled and fuel soaked from not sparking. That was not the case. There was no sign of fuel on the plug; it wasn't wet. In fact, the lead was almost a eggshell-white, rather than a normal condition brownish/tan color. I then pulled the neighboring #4 plug for a visual reference. That one was, in fact, a normal color.

So, I now have to believe that my misfire isn't ignition related. The signs (to me) point to a sparking plug but no or very little fuel, making in burn very lean. The only thing I can think of is a faulty injector. I tried running Seafoam in the fuel as an injector cleaner, but it has made no difference yet. I cleared the code, then drove it around hoping for the Seafoam to work or for the code to be thrown again.

Well, after abut 125 miles, the same P0305 code popped up again. It's the only code being thrown, so I have to believe that the issue is concentrated around #5 only.

So, does anyone have any insight as to what else I should try? Or am I looking at replacing a fuel injector for certain? I can't imagine that getting into access them is easy. I looked it up in a Haynes manual that I found in a junkyard - on the 4.0L, the upper intake has to be removed and the fuel rail is sandwiched in between that and the lower intake. I also found the general-purpose removal instructions that were posted last summer, but they didn't look like they referred to anything specific to working under the cowl of an Aerostar. Any advice on that? Any thoughts as to were I can get a reasonable price on injectors?