My 98 chevy k1500 5.7 vortec started up fine i put it in reverse to bak up when i released brake it died an started bak up fine a few days later i died while driving so i replaced battery an altenator it started rough seem to idle ok all gauges fine put it in reverse and gave it gas and it barley acceled put it in drive and gave it bout half gas and very low accell and high rpm sounds like i should be goin fast

SOURCE: Loss of power

Do you know how check if every cilinder is working? with the engine in idle, go to the distribuitor cap and carefully unplug one at the time, every cilinder spark plug wire,in the cilinder you dont see a diference in rpm variation, that cilinder is not working, replace spark plug, if you see spark jumping fron the distribuitor cap torch the spark plug wire, another cause to a cilinder fail could be a loss of compression in one or more cilinder

SOURCE: 1996 gmc k1500 4x4 5.7 vortec motor no start keep

Replace the coolant sensor on the front of the intake manifold.The coolant sensors on this engine does go bad and wont set a check engine light. The sensor will read about -32 to 0 degrees when they do go bad. The computer thinks it is that cold and sends tons of fuel to the engine. If you try to start the engine with the throttle depressed to the floor it puts the fuel system in clear flood mode and wont fire the injectors. Engine will start then and run very rich. The coolant sensor has two wires on it and sometimes you need to replace the wiring pigtail going to it as the sensor can seep coolant into the connector and corrode the terminals. All the parts are available at pepboys and autozone or napa. Good luck