5.7 Loses Power, Does Not Throw Code?

'98 'burb K1500, 5.7 Vortec, 185k miles.
After driving about 30 miles at 60-65, was coming off an on-ramp pedal-to-the-metal in "high" range on the trannie, and found
myself doing 38 mph with the engine at about 3,000 RPMs.
Backed off the throttle, nursed it up to sixty.
Tried giving it more throttle a few times and got similar results: engine seemed tb missing, RPMs rose, but no more speed. It even choked enough to lose speed sometimes.
Backing off and carefully re-applying lesser amounts of throttle would get it back up to a higher speed.
Limped home, popped the hood while the engine was idling to look for sparks and listen for noises; engine died after a couple of minutes at idle.
Let it sit overnight before turning it over to a shop.
Shop ran it 20+ miles with a computer plugged in, but couldn't provoke the problem or find anything abnormal.
Changed out the fuel filter just on GPs, said the filter was a little clogged, but not enough tb a problem.
Fuel pump has been noisy last few months, but they said fuel pressure is OK.
The mystery seems to be why it never threw any kind of code.
Anybody have some thoughts?
--
PeteCresswell

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(PeteCresswell) wrote:

Sounds like it could be a weak spark
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My thoughts would be the fuel filter, which you have since changed out. Sounds like classic fuel starvation to me.
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Fuel pump.
My old Taurus did the same, after fuel pump got hot it lost pressure. Gradually got worse and worse until it would not even idle the motor. Unlike my '99 Yuk that just died after a 10 mile warning. That pump was noisy for a while though. Fuel pressure gauge is a necessary tool nowadays. No code will be throw as it's not a misfire as all cylinders loose evenly not just one or two. There are no fuel pressure sensors in the system
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Per Repairman:

You and Augustus have convinced me - especially in light of the pump having become a *lot* noisier over the past months.
That, plus hearing from the shop that they start getting more failures as the weather heats up.... and imagining how stupid I'd feel stranded 100 miles from home if/when the thing fails....
$500 for parts... sheesh!... you'd think the things would last a lot longer than mine have. I think this will be the second replacement.... maybe the third.
--
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Got my Yuk with 30k on it, pump went at 110k . It was noisy from day one when I got the truck. That makes me think the first owner ran the tank down all the time. My work Chevy van has 174k mile on it with the original pump, it never is let below a quarter tank of gas. That pump is quiet. Only reason I think it lasted that long was that I followed the serv. manual and changed fuel filter every 30k miles and never let the tank go lower than a quarter tank. Fuel filter is small compared to some other brand vehicles, at least on this vintage of GM trucks. Cost me $525 to have it done 2 yr ago as I was 250 miles from home when it went in a snowstorm.
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