you might want to do a coolent pressure test if it is hard to start when warm. head gasket might be leaking into cylinder 5 when warm.

 

Stay focused on carbon removal with additives along with TOP TIER GAS.
Plus monitor the ECT sensor on your scanner also verify integrity around the engine coolant system with a IR TEMP GUN!

DON'T OVERHEAT!

 

Hope that's not the case, I'd expect to see other signs if head gasket was leaking. So far no smoke in the tailpipe, no signs of coolant in the cylinder (checked using a snake cam), plugs looked normal across all cylinders, oil analysis came back normal with no signs of coolant in oil, I've also done combustion gas test to see if any exhaust was present in the coolant. Tested cooling system again today via pressure test and it holds 15psi no problem.

I read somewhere that it could be sticky valve 🤷

 

Well no luck with the rough start, truck is definitely running smoother and feels great after all that seafoam and various parts. I went ahead and replaced both cam sensors since they were inexpensive, no change. Still get the intermittent rough start or no start at all, it's weird. Always starts the second try or when the truck is completely cool, even when at full operating temp it starts right up. It's only after it's been sitting for 10 or some minutes, like when I go to the store does it happen.

Checked fuel pressure 50-55psi with key on start, 60psi engine running. Once shut off fuel pressure remains 50-55psi takes a while to go down.

Actually ran across this video with Dingle D H3 Humper, literally my problem.

 

And this was his fix

 

Yes this is what led me to replace my camshaft sensors. His problem was that his cam sensor was not properly seated. Not the same issue, but symptoms are similar.

I'm now thinking maybe my purge valve is stuck open allowing vapor into my intake manifold while the truck sits there after running. But I think I'd notice other symptoms if that was the case, fuel smell, negative trims, but I'm not seeing that. My other thought maybe it's the crankshaft sensor???

 

 

I've found a lot of threads regarding the anti theft system, doesn't quite fit my symptoms. I don't see the locking light and it doesn't disable fuel for 10min - my symptoms only happen after the truck has fully warmed and if I let it sit for 10-20min. Also starts up on second try every time.

 

That would for sure throw a code with CEL.

 

From what I've read is that often a crankshaft or camshaft sensors when failing don't trigger CEL, it produces intermittent symptoms similar to mine. Same with purge valve, it doesn't always meet the criteria to trigger CEL. Purge valve should be easy to test by disconnecting it from the TB and seeing if it gets rid of the occasional crank no start or long cranks and stumbles after heat soak.