Riddle me this... hot start 'N dies, miss / cut out only in summer

[97K1500Silverado]

Starts right up when cold and runs excellent all winter long and short trips around town. smooth and powerful from idle to redline.

The problem is during summer after a 60+ mile highway drive, It will run great the initial drive until shutoff. When trying to restart it cranks a bit longer, fires, revs up (as usual) then dies. Have to crank awhile and manually give it throttle so it stays running. Will run slightly rough from idle to redline, cuts out if you mash the gas or even smooth gentle throttle inputs. Definitely a miss like electrical or no fuel? Once you let it cool down for at least an hour, it fires up, revs, idles fine.

This was a once a year random problem only with the hard starts when warm. This year is the first time it has missed or cut out throughout the RPM range after a heat soaked hot start

NO Service Engine Soon light.

What do you think the problem is?

Anyone experience something similar?

97 K1500 Vortec 5.7 Black Bear Tune. 210k miles
original poppet spider fuel injection
Fuel pump (2nd time) replaced 30k miles ago with Delphi pump along with new fuel filter
New plugs, cap, rotor, wires 20k miles ago
New Bosh O2 sensors (all 4) 20k miles ago
New high flow catalytic converters 20k miles ago
Engine grounds are clean

 

[Awest623]

Do you have access to a scanner? Even a Bluetooth phone scanner will do. You can pick one up for $12 on amazon

 

[Awest623]

Also do you have any way to verify fuel pressure? Is spark firing properly?

 

[HotWheelsBurban]

Check all your wires and connections. Could be bad wiring or connections on the module connector, or a battery cable that has unseen corrosion. Both known issues on these trucks. Also check the starter and its terminals. Hot no start can happen from oil or greasy slime getting into the starter. My 99 Burb 5.7 vortec ran like its usual champ self until a couple of short hop trips. Wouldn't start for nothing, then after we called a wrecker and it had been sitting for about 3 hours, sumbitch fired right up! I took it apart down under and pulled the starter. Also inspected all 3 cables. Could also be the crankshaft position sensor going out gradually. Till you can pull some data on it, you're going to have to do a process of elimination....good luck and post updates with the eventual solution

 

[Pinger]

Do these trucks have a fuel pressure accumulator? If so, go straight there.

Sounds as if fuel pressure could be leaking down and allowing the fuel to vapourise in the line and causing an 'air' lock. If so. it will be at a high point where the 'bubble' can't be pushed down to continue the flow (top of manifold?). Try swaddling there with rags soaked in cold water the next time it happens.

 

[mtl111]

I'm wondering if its not a heat soaked coil and/or ignition control module. You didn't say you have ever changed these so I assume they are original. A scanner would definitely be helpful.

Sent from my SAMSUNG-SM-G930A using Tapatalk

 

[guyopel]

Sticking EGR valve that is almost closed but stuck just open enough to drop vacuum and cause hard start (low vacuum) and low speed skip with no codes. HTH

 

[97K1500Silverado]

I'm wondering if its not a heat soaked coil and/or ignition control module. You didn't say you have ever changed these so I assume they are original. A scanner would definitely be helpful.

Sent from my SAMSUNG-SM-G930A using Tapatalk

Forgot to add in original post that coil and cap replaced 20k miles ago.

Don’t think I’ve replaced the ICM. I’ll have to take another look.

 

[97K1500Silverado]

Do these trucks have a fuel pressure accumulator? If so, go straight there.

Sounds as if fuel pressure could be leaking down and allowing the fuel to vapourise in the line and causing an 'air' lock. If so. it will be at a high point where the 'bubble' can't be pushed down to continue the flow (top of manifold?). Try swaddling there with rags soaked in cold water the next time it happens.

Vortec trucks have a fuel pressure regulator under the manifold cover?

Truck had the infamous intake manifold gaskets replaced 50k miles ago. Not sure if regulator was replaced at that time? Prob not.

Would a malfunctioning fuel pump relay cause this issue? Or is that really only used for startup?

 

[HotWheelsBurban]

You can check the relay by seeing if another one in the underhood fuse panel has the same pins. Swap them and see if the problem persists. If that's it, a new relay is under 30 bucks IIRC. Replaced it and starter relay on my Burb but not sure if either was really bad. Both were likely the original ones though so after 20 years probably due for replacement. My other 99 Burb had fuel injection work done years ago; I think the fuel pressure regulator was one thing changed. The spider upgrade wasn't available then, so I know 2 separate injectors were bad and replaced. Also upper manifold. Seems like the bill was around a grand.