I HAVE A 1995 S10 4 CYL.MANUAL SHIFT WHEN I START IT IF I TAKE OFF QUICK IT WILL IDLE NORMAL WHEN I STOP BUT IT I SIT AND LET IDLE IT WILL CLICK AND AND SPEED UP BUT ON THE ROAD IT RUNS GREAT

you are stopping the vac process and inter rups vac it does shut down if you remove any vac line

Wrong fuel octane water in fuel...

your thermostat might be stuck open so while idle it can warm up but as soon as the motor increases speed it cools down quick

No. The jeep moves when starting the engine as if the clutch isn't fully engaged, but only then. Sitting idle with the clutch depressed it is fine.

with switch on, the transmission will not shift into 1st gear--it will start in second and then shift to third, etc.. This is OK for normal driving, but not if you start on hills or want to accelerate quickly from a stop.

you need to replace the neutral starting switch on the transmission,it is a screw in type and has a connector with three wires on it,or start your van in neutral.

Ford : back the truck up 10ft put truck in neutral and disengage four wheel low. (You can't drive in four wheel low cause its a pulling gear and you won't do over 3-5 mph.)
Nissan: start truck see if it idles normal. If so rev motor and check throttle for sticking and check EGR valve make sure its not stuck open or malfunctioning when you drive it..

check the belt timing. could be firing early or late.

I need to get a clear mental picture of what exactly is happening.

With this said, you stated that the car "runs fine" until warmed up.

Q: When you start the car when cold it idles fine?
Q: If you allow the car to idle until "fully" warmed does the car stall?
Q: As the car begins to warm up, Does the RPM fluctuate abnormally?
Q: Does the car Only stall when you press on the gas pedal or does it stall just sitting and idling in addition to pressing the gas pedal?
Q: If you can drive it while cold does the car stall during acceleration when warm or only at Stop Signs / Lights?
Q: If you wait 20min or so, can you start the car again?
Q: How many miles are on the car?

I would the oil level in the tranny.mabee from sitting some leaked out.But i would add the Lucas as soon as i could.