With a lot of Olds'88 parts/sensors/wiring updated, the car runs into a suffocation condition after making 300-500 miles, sometimes less, when it appears it is suddenly starving for fuel. From this point on it'* not driveable. It'* so bad I can mark a potential spot on the map where it may fail, and I will have to drop off, or clog everyone behind me.
New fuel line components/filters, O2, vacuum leaks checked, MAF, cooling system, switched ECUs.
Other shop opened the exhaust - found nothing caked there as well.

What can possibly warm up after such a long drive and completely destroy you? V6 is going up the steepest hills like a champ.

Also, this problem is brand-new. Folks who ran it with a scanner reported drop in fuel PSI and fuel volume, when then were able to reproduce.

Usually occurs for the first time when getting off idle or at very low speed; often going into incline.

Ideas for this sudden-death after a longest-drive would be appreciated. Prior to this would make 1,000 miles without a nick of stalling.

Off the top of my head I'd say a fuel pressure issue is likely.

Is this the 1988 Oldsmobile Cutlass in your profile or some kind of Oldsmobile 88?

^ I agree.

What is the history of this fuel pump? Fuel filter?

If the history is unknown, I would at least start with replacing the fuel pump and filter.

Put a fuel pressure gauge on it. Likely the fuel pump.

Fuel pump, fuel filter and fuel pressure regulator have been replaced just recently.

Since this is an FI engine, what are the odds this might be a vapor lock?

@CathedralCub, just realized there is Olds 88, but this one is an 88 Cutlass.

In couple cases I was able to move it while high-revving in moving state (hitting ~70mph). After 5 minutes of resistance, condition suddenly goes away and the car carries me anther 100 miles, no problem.
But sometimes it keeps stalling and stalling to the point I have to park on the side and leave the car alone. After 30 minutes or so, it would start and move like nothing happened.

Well we know it'* a Cutlass and it'* a V6 but year might be nice.
Without taking a pressure check while it'* struggling you don't know for sure that the new pump is actually keeping up.
You have to start somewhere and that is the best.

I replaced a fuel pump in a Blazer years ago with a cheap POS Airtex brand pump. 6 months later, I had to replace it again.


Like Carfixer suggested, I would verify fuel pressure cold. Then find some way to mount the gauge so you can see the pressure when you expect the engine to start failing.

You can get a long hose for the gauge. We just tape it to the windshield and watch it. Catches problems like this.

We actually did this - and fuel PSI dropped during these moments on two different pumps. The question I have here is - "but why?", and what can be behind this situation after having driven for 2+ hours in a normal fashion.

UPDATE after 3 more months of agony

The Beast is back on the road, 1,000 miles later on a rugged terrain.in the mountains, it roars and runs on full V6.

The winning combination was:
* changed the fuel pump, twice (good idea Mike of Arizona)
* changed the fuel pressure controller
* found a vacuum leak during fog test, replaced the throttle body
* replaced O2 - just for the party

There is still hesitation, and it stalled twice on me, this time on full idle, but going uphill like Lance Armstrong, or running in traffic or 8 hours straight on highways in changing elevation is no longer a problem.

That was one rough Y2022.