What could cause a 2000 Chevrolet Impala not to start when hot. Some of the things it's doing when trying to start is, runs momentarily then stops, sputters, no acceleration when it starts before it quits running, etc. But, then after it has set for few hours (I'm assuming it is when the engine has cooled down), it starts and runs. One additional note is on a couple of occasions, first thing in the morning it has kind of sputtered, and once it has rev'd up momentarily for a second, when started.