1999 Chevy S-10 Engine Missing during Idle and at speed

Have it down to injector wiring harness or pcm at this point. The P0300 code goes away when the #1 injector connector is removed from the injector. Did a noid test and got blinking from injectors 2, 3, and 4. Got nothing from 1. No distributor on this truck. There is a Iginition Module, 2 ignition coil packs then the spark plug wires and spark plugs all of which have been changed. Thanks for the info pear69

Checked injector wire harness. Wires were ok. Checked resistance in wires between 5 pin connector ( where the injector harness connects to the wires that run to the pcm) and the pcm. Received open results through all pins in pcm. Tired another wire to see if this method would work and found the wire with resistance. Conclusion I came to is a broken power wire for injector #1 between the 5 pin connector and PCM. Taking to repair shop tomorrow for them to fix broken wire. Sorry I'm not much of an electrician and feel the repair is beyond my knowledge. Thanks for the suggestions and Help, Just wanted to update you all on what I found to be wrong in my case.

It's possible that it is the ground wire. There is one common wire to all the injectors that I assumed was the ground and the wires that were specific to the injectors was the power. Though it is very possible that it is the other way around. I am not much of an electrician so its extremely possible that I have the power and ground wires confused. I do know for a fact that the wire runs from pin B of the 5-pin connector to the PCM so that information should allow me to explain it to the service center so they can fix it. Sorry if I confused it, and thanks again for the help.

Thought I would update the fix on my truck for future referance on the site. It turned out to be the PCM that failed on my truck. It was changed and programmed and now it runs as good as ever. Thanks for all the help.