'85 244DL LH2.2 B230 M46 169k

Just when I think I have it fixed, it stalls again and maybe even leaves me stranded...

I've gone through everything, yet I'm still having the same problem: starts cold, idles low (TB adjustment makes little difference), runs for a minute or so, stalls like turning the key off. Usually restarts, usually stalls quickly. Sometimes it almost stalls, then comes back or can be saved by flooring it. Once warmed up, it has never stalled on me and runs great, I've driven it up to 30 miles at a time. When warm, it will restart but possibly stall. It has to be electrical/ignition related. I have same symptoms if 4 and 6 are jumpered. Fuel pumps are still running briefly after stall. It will NOT start at all if AMM is unplugged. I do have lots of fuel in the tank, and lift pump is in good order. Filter is new. Coil tested good before and after stall. 12V to computer before and after stall. Hall sensor tested good. I have spark before and after stall. Plugs, wires, cap, rotor new (all Bosch now). ECT tested in spec when cold, haven't tested when up to temp. Voltage to knock sensor in spec and tightened, IAC cleaned and tested, ECU new, wiring harness new, TPS tested and adjusted properly. I went through every harness plug and cleaned and bent the connectors. Timing belt new, installed properly.

It is running rich cold and warm. Tailpipe is black, exhaust is slightly moist. I can smell it, even when warmed up. I have reason to suspect that the thermostat is bad, and it will be replaced. But that is not causing my stall when still cold. AMM set at 300 ohms. Oxygen sensor puts out .5V at startup, but I haven't tested it warmed up. Again, I don't think this is causing the stall. Plugs pulled immediately after stall: not fouled, slightly dark, still spark.

I feel like something is happening when the computer switches from open to closed loop operation, but I could be wrong.

What am I missing here?
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1980 244 diesel M46 168k, my 4th 240