1987 V10 305 TBI - Good until it just falls on its face.

[rdhill10]

I have a 87 Chevy Silverado V10 with 305 TBI. I've replaced IAC, MAP Sensor, rebuilt TBI with new gaskets fuel regulator.
Tried my best to reset the IAC to instructions found online. I see the IAC pintle when looking into throttle body so thinking thats
what should happen when jumping ALDL pins A & B for 30 secs or so. Engine cranks and starts right up idle seems good isn't
missing as far as can tell no issues. At times though while idling with no stumbling or anything the motor just dies. I mean it
dies like you've hit the switch. While sitting there wondering what the heck just happened I can hear what I think is the IAC
clicking trying to adjust (at least thats what I think I hear). So after stall or dying if you try to restart it will not start however
if I get on the throttle and hold down while starting it will eventually start back up....a stumbling back up until it smooths out.
What's weird is after this happens....say the next morning or whatever if you try to start it up it fires right up no issues until at some
point it does this all again. I plan soon to look at vacuum lines very closely and I still have my eye on the IAC just cant tell if its
doing what its supposed to be doing. Would appreciate any suggestions or directions with this narrative? Definitely can't trust
to drive at this point you never know when the next dying of engine will happen. One other item like to mention when its up
and running I can get all over the throttle and responds very well...no back firing, stumbling anything.

Thanks to all for any suggestions

 

[Smtty58]

Fuel pump, fuel pressure? Instant shutdown sounds like ignition though.

 

[rdhill10]

honestly i have a fuel filter ready to install so going to try that for sure. Also the distributor and ignition module are fairly new.
Also read that's a high probable failure point. The last episode didn't trigger service engine light but a prior time i had codes 33, 42, and 44.
So definitely can't rule out the ignition module....i do think strange that as soon as it happens I can get it started again just have to stand on the throttle.

 

[gmbellew]

I’d look very closely at the plug wires, distributor cap, and rotor. Could be stray voltage if the ICM is ok. Wires with cracked insulation, cracked cap, bad cap terminals, loose rotor under the cap, etc can all send stray voltage that will zap ICM wires and kill the engine like an ignition problem.