Okay, this may be a long post so apologies in advance.
I have a 94 1500 with the 350 TBI. I have owned this truck a little over a year now. I bought it with a blown motor because P.O decided to run it hot and then put water in the coolant and it froze and busted the block. Regardless, found a really clean re-manned motor from a 95 tbi at the junkyard. Replaced every seal and gasket, other than head gaskets. Well the truck runs and drives of course, has good oil pressure, however, it takes it a couple of extra cranks to start, and then on top of that, it has a random / slight misfire only noticeable at idle. Well, this is where the fun begins. Here is what I have replaced with either new or used (verified working) parts...
New 02 sensor
TBI rebuild kit
Distributor with new cap, rotor, wires. (Used delco plugs gapped appropriately)
Timing chain
Coolant temperature sensors
IAC valve
MAP sensor (Keep this part in mind for a second)
New complete fuel pump / sending unit and new fuel filter
Ignition coil
Now here is the fun part. A couple of weeks after replacing the o2 sensor, I was leaving work, started the truck as normal, and about a minute or so later, truck dies. Cranks, but no start. Waited a few minutes, truck started back up and ran like it normally does. Didn't think to terribly much about it. However, yesterday. Was driving it home from work, was working like normal, then just dies again. Okay... odd. Try to start it, cranks, but thats it. Checked fuel pump fuse, checked distributor wires, checked all sensors were plugged in. Nothing. I walk a little over a mile back home, grabbed some starting fluid and drove back to the truck. Got in it before doing anything, truck starts... dies 30 seconds later. Start it again, i'm able to rev it fine, as soon as it goes back to idle, dies again. Wouldn't start again after that. Tried starting fluid, it fires but immediatley dies again. Left it for about 10 minutes, (checking my phone for ideas) try starting it again and it runs and gets all the way back home and hasn't died like that again.
So here is where i'm at today. I have the truck up to temperature. Idling rough-ish like always.. Timing is correct btw. I unplug the MAP sensor.. truck runs extremely rich. HOWEVER, idles and starts perfectly like a new truck. Changed with another MAP sensor. No difference. Checked the voltage to the MAP sensor, getting 5 volts without engine running which is were it needs to be, so connector is out of the question. Changed over to another TBI unit thinking maybe I had bad injectors. No difference. However it hasn't stalled again, but I haven't really drove it.
So at this point i'm at my wits end, I've checked vaccum lines as well, everything seems fine. No intake manifold leak or anything. Does anyone have an idea, of what else it may be. Because I'm about ready to slap a blue oval on the grill of this truck... if you catch my drift.
Thank you guys in advance, and again. Sorry for the long read / rant.