Welp, take a look at (http://www.brickboard.com/FAQ/700-900/HotStartProblemQuickReferenceGuide.htm) as well as the greater (http://www.brickboard.com/FAQ/700-900/).
XXX Have done that and distilled it into the questions I asked and the areas I am looking at, actually.


You can damage the AMM (or MAF) sensor by unplugging/plugging with the engine running. Possibly the fuel control system computer, too.
XXX Thanks-Beside the previous poster, I have seen that recommendation before.

Air (vacuum) intake leaks?
XXX I already instructed son to check spraying around gaskets and such. If there WERE a leak, I suspect it would create a lean mixture that would cause a "miss" at idle rather than a wandering rpm, but you never know. Also having to crank a hot engine w/ open throttle would appear to suggest too MUCH fuel and not enough air, but again, hard to say.

Faulty engine control systems coolant temp sensor.
XXX ECT was my first thought at hard-tot-starting (too much fuel), but now the problem has progressed quickly to unstable idle, and stumble when changing the idle-load on the engine.

Fuel pressure regulator leaking fuel into the air intake port (manifold).
XXX Never thought of that w/ a bad regulator diagphram. Will check that one for sure!

Also, PLEASE (http://www.brickboard.com/FAQ/700-900/EngineOBDCodes.htm)! Check them codes!!!!!
No codes shown. I understand codes will only show if the "Check Engine Light" is actually displayed, and they go away when the light goes out (UN-like OBD II systems that retain a code)?? Can you verify that codes ARE retained even if there is NO Check Engine Light illuminated?
XXX BTW, here is the only chart showing codes (copy/paste):
http://screencast.com/t/UWmfWNMXd1
Are there more codes possible than this w/ LH2.4?

The 700-900 air box also has a flap valve that controls whether air intake comes in fresh of off the exhaust manifold pre-heater intake as controlled by a sping loaded thermostat. At least disconnect the pre-heater solder accordion hose from that shroud pre-heater plate on the exhaust manifold.
XXX Easily done.

Clogged fuel filter. faulty injector relay, fuses, weak fuel pump(s), leaking injectors ... and on and on. Search the brickboard. Check them OBD codes and report back!!!!
XXX- Clogged fuel filter: Replaced 300mi ago after tank flushed and new Bosch fuel pump/filter installed. Plus, if it were clogged, I doubt it would run perfectly under load at any driving speed when fuel demand is MUCH higher than at idle?
XXX Injector relay. Again, would it run under load at 60mph if the relay were faulty?

XXX Thanks, Bob

IS there a start injector on the LH2.4 system? I cannot find one. Some diagrams say "yes; others don't say "yes/no."