I have a 94 k1500 Z71 and have the same problem. Do you smell a "rich fuel" exhaust smell when this happens? Also when you first start the motor after setting and at idle does the exhaust smell rich? I have been trying to correct this problem for a year now and have replaced almost ever part related to fuel and ignition with no luck. My next change will be computer ECM. Does anyone know if there is a pressure bleed off on the fuel pressure of these trucks when the key is truned off?

 

is it a vortec engine

 

No, it is a standard 350 with TBI

 

yes it is the vortec engine

 

I had this hesitation problem I found out it was the computer. Actually it was a very easy fix. First I had codes which said that my O2 sensors were bad all three of them. The biggest thing going on was a hesitation upon acceleration And finally chronic stalling.

look for where your computer is on your vehicle. If your computer is placed underneath your brake fluid and power steering fluid reservoirs. That may be your problem. If your computer is located there gm had a chronic problem of corrosion which literally breaks the bolt heads off the Computer housing and allows moisture to get inside the computer and causes computer failure. Furthermore, the wire harnesses which attach the computer also corrode which wreaks havoc with half a dozen different systems.

When I removed my wire harnesses from my computer the bottom two harnesses were extremely hard to remove and one of them was literally fused with the computer( also called pcm or ecm)...

If you're having a corrosion problem I will make this warning to you, the top two wire harnesses on my computer came off freely both the bottom ones were stuck due to corrosion, one wire harness was destroyed when it was removed. This is very common if you're having a corrosion problem.

LISTEN TO ME CAREFULLY, when I went to replace the wire harness I cut off my old wire harness by cutting all the 25+ wires at one time. This was a massive mistake. Because after I had removed the old wiring harness I realize they were several of the same type of wires on that harness several green/white stripes several green/black stripes and so on. You can pop open the back part of the black wire harness and open it enough to see the very small numbers of each wire number one through 32. Use a piece of masking tape and Mark each wire that has a duplicate colored wire, mark each wires position on the harness number. Or you can transfer one wire at a time to the new harness that is probably safer.

A used computer cost Only $85 and it came programmed. I got it off of a online auction website