89 S10 4cyl idles but when in gear stalls

89 s10 4cyl. idles even when reeved but when put in gear to drive goes about 100 feet then stalls. restarts right a way.

Check for lose of fuel or spark when it stalls.

I had that motor in an '86 Cutlass Ciera and it would start & idle good but would die when you put it in gear. It also would not idle up or even maintain idle speed when you turned on the air conditioner. The idle air control was ok.
Turns out the computer didn't have the crank position for reference because of a bad module in the distributor and it's sealed so I replaced the distributor with a new Delco to fix it. A coupla years later it happened again...bad distributor again. Another new Delco and it's still going 5 years no problem.
The young'un says the Check Engine light would come on after the engine died...I don't remember.

Try fuel pump pressure