No easy fixes? Amen brother.
I got this one beat today, not but a few hours ago on a hunch.
Most of the problems suggested here were ruled out. The first "guess" we put in was plugs, wires, and a fuel filter. The fuel pump was replaced based on the low fuel pressure at the rail, and the fuel pump relay bypassed via a switch and wires run directly to the sender due to insufficient voltage readings at the sender. This could have been the cause of the low pressure in the first place, but the pump I took out of the Heep (an aftermarket replacement pump) had no sock on it, so was probably not going to be long for this world anyway. The TPS checked out, the IAC was clean and the port clean (recently replaced in fact). MAP sensor had the correct input voltage, the EGR valve had long since been blocked off, and we have white hot spark. The distributor appeared suspicous, and the firing order is different from the factory specification, so a timing issue would have been a good place to suspect.
Still, I felt based off of some experience and a bit of a hunch the the issue was in the MAP sensor - also making it a bit of a timing issue in a sense as well. So pulling the MAP sensor from Tlowery04's totaled jeep, I walked resolutely over to the Heep but then remembered an important point. During our initial diagnostic tests I had taken the connector off of the MAP sensor and tested it with a multimeter to see if it was recieving the correct voltage from the computer. At that moment, I had the epiphany.
At some point, your's truly, Captain Retard here had reconnected the MAP sensor
BACKWARDS.
So I won a mixed victory, as the Heep now runs very well overall (still a few minor loose ends to tie up), but I was at the same time humbled by my inability to figure the correct orientation on the MAP sensor connector.
In my defense, it is a small consolation that the original owners had broken the clasp on the connector quite cleanly, which made it difficult to really figure the correct orientation once the connector was removed for that first round of diagnostics.
That concludes my long winded story. Maybe some day somebody will search the forums and find they made the same stupid error I made, which would make me feel a whole lot better about myself, frankly.
)