1993 c1500 dies while idling

a vacuum leak. cold fuel system is enriched. any extra load could cause it to die. what TL? 2.5? idle air control valve? TPS ? check for codes!!

you have probably knocked somewires loose like cam sensor or crank sensor re check all your wiring near where you did all the work..

No read the fix below.

Engine stalling issue at low speeds

This problem is commonly caused by a dirty automatic idle speed control valve and throttle valve. Buy a can of throttle valve cleaner from NAPA or Carquest (made by CRC chemicals) and spray it into the air intake while the engine is running, use up about 1/2 the can, engine will try to stall hold the speed up, shut it down and let it soak for 30 minutes, restart and blow out the remaining fluid, shut it down and disconnect the negative battery cable for 5 Min's to reset the base idle control

Please replace your COIL with new one.
Regards, Jay

How is your oil pressure sender?? The fuel pump runs thru it after start. Watch the gauge while cranking It may give indication

If the engine starts and runs fine in Park, try Neutral as well. If it runs and holds steady IDLE at both positions the issue is with your transmission. In the C1500 silverado series/GMC they had a period of bad trannys. In your case it sounds like the torque converter has gone bad and basically when you engage in gear its preventing your engine from turning over, thus the die. Its an easy diagnosis using above, but the fix is costly. A new transmission for these trucks run about $2300 or more to be installed. If you are able, a local mechanic may install a used one from a junk yard a lot cheaper... issue is there you have no warranty. So if this is an everyday driver/primary vehicle I would trust a transmission shop. Otherwise find your local trusted guy and ask them about a second hand job, or a rebuild.

You either have a bad Idle air control valve or your injectors are clogged. Try turning the steering wheel and turning on the AC and fan. If the idle goes down the IAC is bad. A normal IAC should raise the idle a little then settle when a load is put on th engine.

Off the top it sounds like fuel filter. Without any other information that's what I would suspect

Sounds like a poor idle. try adjusting the idle screw.

Is the engine at running temperature when it starts running rough? And when it is cool does it run fine until it warms up?