pulsing/powerloss

i have a 2001 silverado with 5.3l. this problem started over a period of about two weeks. it will run fine at normal easy driving. if you need power like to pass or go up a hill and really get in to the gas it loses power and starts pulsing like you are working the gas pedal up and down and the check engine light comes on. it runs like this even at normal driving after it gets the check engine light. if you stop and shut it off the light disapears and it will run correctly until you get into it again. then its the same senario. thanks for any replies, bill

i have a 2001 silverado with 5.3l. this problem started over a period of about two weeks. it will run fine at normal easy driving. if you need power like to pass or go up a hill and really get in to the gas it loses power and starts pulsing like you are working the gas pedal up and down and the check engine light comes on. it runs like this even at normal driving after it gets the check engine light. if you stop and shut it off the light disapears and it will run correctly until you get into it again. then its the same senario. thanks for any replies, bill
The first thing you need to do is have the code read.
You can have this done at some of the chain parts stores like Autozone.
Post the code and we can go from there