Low engine power warning came on and the would not accelerate after truck warmed up it was fine... it's a 03 silverado

could be low float level, low pump pressure/supply
blocked fuel filter
when cold the engine is running on choke setting which draws more fuel from the carby
when it is warm the choke is off and if you have a flat spot ( (sputter) , that indicates a lack of fuel or maybe a bad accelerator pump or power valve
if the carby is a holley then replace the power valve and overhaul the accelerator pump.

You are going to need to have the transmission rebuilt.

The problem could be the vacuum check valve that keeps the vacuum in the system.

I stopped to assist a gas powered Winnebago stuck on the highway a while back. The engine would run but not produce much power or rpm's.

The problem turned out to be a plugged muffler which seriously reduced the air flow to the intake system and as a result the power and ability of the engine to rpm's or power.

As modern day vehicle engines are computer controlled there could be systems that are not functioning properly...which should log a code and activate a warning light on your dash board. ODBII diagnostics is always the first step to take when trying to isolate a fault.

Mine did the same thing this morning. I was on my way to school when it started sputtering, so i went to the store to put gas in it, because it was kinda low. Then when i went to start it up to leave the store, it was dead, so i got a jump. Then when i went to go take off it took forever to accelerate, and it would only top out at 15mph. Have you fixed yours yet? Im thinking it may have something to do with the battery or alternator

I am having the same problem but it only happens to me when the car engine is cold. This does not happen when the car has been on for a while. My solution is that I warm up the car for about 20 minutes before driving and my car works fine.

Added to my problem, when I press the gas, it asks like it's choking and I have to press through it, flooring the gas, to which it accelerates too much. It's ok when no in traffic. Also, when I stop the car idles really low and acts like it wants to shut off.

Sounds like an igition switch to me, with the discription you are giving.

DOES IT HAVE A LOT OF MILES ON IT OR MAY BE THE OIL PUMP IS IS GOING OUT? THERE IS A SPRING IN THE PUMP THAT IS A BYPASS FOR HOW HIGH PSI IT MAY HAVE BROKE THAT WILL GIVE YOU LOW PSI.

I had a power problem, when cold idled just fine,when warm it would miss at idle, spudder on acceleration and sound just fine at higher rpm. found number three spark plug wire had burned through lower boot. Spark was firing to head at low idle. same wire burn twice with about 40000 mile between.

my 2003 f-350 6.0 has a 110 volt plug that i plug in at night so by morning all fluids are warm and no more lack of power when u need it remember its diesel no spark so that oil has to reach a warmer temp for the glow plugs to fire this is stock on most mine was behind the passenger fog light area it has a cover