1996 Chevy Astro ENGINE DON COME ON JUST CRANK

YES ACTUALLY MY ENGINE JUST CRANK I OPEN THE KEY AND I TRY TO MAKE THE ENGINE COMES ON AND JUST CRANK, IF I USE STARTING FLUID I CNA MAKE THE ENGINE COMES ON AND STAY ON AND DRIVE IT BUT BUT IF AM GOING UPHILL DON'T HAVE POWER I CAN PUSH THE PEDAL AND IS NOT RESPONSE, DOWN HILL NOT A PROBLEM IT ALL AND I CAN GO 80 MILES X HOUR IF I WISH, AND WHEN I TURN THE ENGINE OFF AND I LEAVE IT STAND FOR 10 MINUTES DONT WANT COME ON AGAIN I GET THE ENGINE CODE BUT AM CONCERN WHAT COULD BE IS THE P0306 I HOPE SOMEONE CAN GIVE AN ADVICE I APRECIATE ANY HELP POSSIBLE AND THANKS IN FORWARD.