i have a 2005 chevy venture van with a 3400
sfi v6, here's the problem the car cranks perfectly and idles great but after driving it for 15 mins. or so the check engine light blinks and it loses power dramatically, the motor idles real rough but does not quit. after turning it off and letting it sit for five mins.it cranks and runs fine until it seems it heats back up and then it does it again. but it does not do it all the time. especially in the morning when its cooler outside. any clues ?????