Hard to start - hunting & stumbling - only when cold.

[stutaeng]

I'm with @alpinecrick on this. The high humidity morning crank-no-start is kinda common on these engines. I had a 4.3 that did this and I never was able to figure it out. It did have an aftermarket distributor my mechanic had replaced around 225k. I was around 260k when I pulled the engine due to low oil pressure.

Towards the end I replaced the battery with the V8 battery and was able to crank non-stop for about a full minute and it would fire. Wasn't ideal, but it worked. Not sure why some engines are affected, the 4.3 is certainly one of them. Or, I applied heat from a heat gun on the cap and it would fire.

I've got another truck with 5.7 and that one doesn't do that. I "think" the distributor and cap are original. I'm too scared to change them, even though I saw the cap had a crack.

On both engines, my static fuel pressure was always around 55-56 psi. I know that's considered low per the specs, but that's what they are on mine. The 5.7 eventually got the mpfi upgrade, but had checked prior and that's what OEM injectors were getting on fuel pressure and it started just fine.

 

[wezmykat]

I got a similar issue on my tbi 94 suburban
Here in Montreal we get humidity from 15 to 100 and it dont make no difference.
Temperature from -30 to 100+ as soon as it gets to be over 60 the issue is "gone" below that, the colder it is, the worse it gets. At -30 the truck will misfire every few seconds.
Once the engine warms up, rpms drop to 600~ issue is gone, no matter the weather conditions.
Now everything thats been posted here, the only thing that makes sense is the intake. Carbon/sludge/crap in there soaks up gasoline for a while until it cant and then air fuel ratio normalises and it runs better, as well as leaks that seal themselves with heat expansion and it runs better.
I've seen a lot of posts & videos of people wasting money replacing perfectly good parts only to have zero impact on the issue.

All you need is 4$ of permatex rtv 6$ of intake gaskets 10$ of spray throttle cleaner 5$ towels and a lot of labor (and probably coolant hoses that will break once taken out) and a lot of patience

 

[Elrey71]

1999 Tahoe with 5.7.

Similar symptoms. Finicky start when cold. Threw a code if cranked for too long. New fuel pump fixed it.