97 7.4 Gremlins
 

My truck has had the hard start when warm issue for some time, but lately it shuts off while driving. Sometimes it would start right away, most of the time I'd have to wait before it would.
I had read where it was possibly the fuel pressure regulator diaphragm allowing fuel in the manifold and since I wanted to change the injectors anyway I did both buying an AC regulator and new injectors from 5O Motorsports.
When I finished yesterday she fired right up, sounded nice. However, I ran to town to fill up the tank and test how it would do and when I pulled into the station it kind of lopped at idle.
I filled it up, started find, then died on the way home. I was able to start it again and drive hone, but went to start it again after a few hours and it would sputter and spit, but not run.
I called my wife out to show her how it was acting and it started up and purred like a kitten.
I did put a new Delco fuel pump and fuel filter in while I was restoring the truck plus I put new wires, plugs, cap, and rotor on while doing the injector work.
Any ideas?

Sounds like a thermal break-down
 

Based on things you did and the way you describe the problem, it appears to be something breaking down when it gets hot. Which is typical of electrical components.

I think it's in the ignition circuit. There are three components in your ignition system that are prone to failure. They are the ICM which gets a signal from the PCM and sends it to the coil to fire. The pickup in the distributor which helps the PCM determine when to fire and the crank sensor (CKP) which basically does the same.

Failure of any one these three should give a CEL. So if the light comes on, you should be checking that first for the code.

Absence of a code then I would go for the ICM first. There is a few ways you could test it without having to just buy one. If it is a hot failure, you could warm it up with a blow dryer and start it up to see if it is having the problem.

Or you could do the opposite by driving it until it fails and then cooling it down with a can of freeze spray to see if it comes back.

You could also allow it to fail and then check for spark.

If it turns out it is one of the other 2 devices, you can basically do the same thing I described for the ICM to those as well.

One last thing, I'm unclear on your engine but on the others, the ICM is mounted with heatsink compound under it. Over time this dries out and should be cleaned and replaced. If you buy a new ICM, they come with the heatsink compound. It is very hard to find now that Radioshack is gone. Most auto parts stores don't have it. But it's worth a try to get.

Don't confuse dielectric grease for heatsink compound. They are vastly different.

Good luck

Re: Sounds like a thermal break-down
 

Thanks for the suggestions. I have a few more nights before I'll be able to check, but I'll post what I find.

Re: 97 7.4 Gremlins
 

Does it get HOT when its loping and struggling to run?

Re: 97 7.4 Gremlins
 

Would have been nice to get an update