Random Hesitated/stumble on start-up

[97SilveradoHD]

so pretty ever since i got the truck, i've been chasing (what seems pretty random) stumble on re-start up. never does it on the first crank of the day, but only after driving around for a bit.
-Turn the key
-Starter cranks normally
-Engine stutters for a sec or two
-Idle picks back up and smooths out
-Drop into park and everything's great

Like i said, it only does this maybe 10-15% of the time, otherwise it fires off great.
New injectors, FPR, fuel pump, fuel filter, No fuel leaks, all new ignition components (still think the problem may be ignition related), new distributor gear, almost every sensor has been replaced (some multiple times)

I'm welcome to any and all suggestions, and i'll do my best to answer questions for troubling shooting

this issue is literally driving me nuts, especially since it seems to like to do it in a crowded parking lot....pretty embarrassing

 

[TylerZ281500]

fuel leak? not used to vortecs but wouldnt a drop in fuel pressure cause a misfire type sound for a bit? id drive it by autozone and get a reader on it or see what codes may be stroed in it.

 

[DAC_CFH]

So essentially you have an intermittent stumble at operating temp. when you first start it? Have you checked for any vacuum leaks? Assuming when you say every component- you also included plugs and wires? HAve you made sure you dont have an ignition wire rubbing on something causing occasional issues? Any valve noise when it first starts?

 

[97SilveradoHD]

no fuel leaks and fuel pressure is good, doesn't bleed down after shut-off.
no valve noise either. haven't checked for vacuum leak but why wold a leak be intermittent? also, the truck idles great, nice and smooth right after the occasional Hic-up...

 

[97SilveradoHD]

bump.

how likely is it that the starter is the culprit? Otherwise, i'm probably going to throw another set of plugs at it and see where we're at. I literally spend a couple hours a day trying to research and/or figure out this problem...it drives me crazy

 

[DAC_CFH]

I would say not likely the culprit
Once it kicks it should be able to take care of itself

 

[97SilveradoHD]

i'm going to check/clean/replace the ground strap behind the motor today.

Here's a list of everything i've done to attempt to fix this issue and others as well:
-New Ls1 injectors
-New Fuel pressure reg.
-All new O-rings and seals on the fuel system
-New Fuel Pump & Filter
-Intake Manifold gaskets
-Distributor Gear
-Cap & Rotor
-Coil
-Plugs & Wires
-New IAC
-New TPS
-New MAF
-Cleaned TB

I'm sure i'm missing something... But everything was replaced with quality brand parts.
Running out of ideas; maybe Ignition module, weak coil, bad wiring connection somewhere, or god forbid something internal in the motor....
-

 

[97SilveradoHD]

just added a new ground strap from the block to a new point on the frame, nice clean solid ground. i guess we'll see if it helps...

 

[DAC_CFH]

The only thing internal I coudl think is if you were to have an issue in the valve train- maybe one sticking or something but normally you will here internals

 

[97SilveradoHD]

well i run 5w-30 full synthetic, so i do hear a little more valve train noise i guess, but nothing abnormal.