Ok, so after a long journey plagued with issues, after I get over one hurtle, I run into another.

After replacing:
Fuel Pump
Ignition Coil
Ignition Wires
Spark Plugs
Distributor Cap
Distributor Rotar
Crankshaft Sensor
and finally a PCM (which finally allowed me to start up the van)
Throttle Position Sensor, next

I can start the van in Park on the first start.
If I put the van into Reverse it stalls.
I cannot usually restart the van in Park, if it does it's a rough start.
I can restart in Neutral without any problems.
If I go back into Reverse, it stalls.
If I put it into Drive, no problems.

Any suggestions? I would appreciate them.



Reading the forums, I found some suggestions but can anyone explain:
why temperature sensor might help? (Park vs Neutral)
why clogged CAT converter might cause problem? (Reverse vs Drive)
Vacuum leaks?

I will try to clean the IAC, because I have some noticeable up/down rev'ing.

 

Clean or replace your IAC, all of your symptoms point to that being the issue.

Bad temp sensor can result in hard start issues but its not common. Bad cat is easily tested by removing the front 02 sensor or drilling a hole before the cat and testing for pressure.

Vacuum leaks will cause rough idle and could give various random error codes as the computer will sense the mix is now lean and add fuel trying to compensate.