When my 2003 grand prix first starts up it jerks and once you give it gas it's fine until you hit 30 to 45 miles an hour and then it starts doing it again. After about 45 mph it runs fine. Any suggestions on what it could be?
the motor mount is bad...replace.
high voltage loss,coil leaking spark, to ground ,could be will show under load more if not i'de say tps, throttle position sw. shorted at mid throttle,codes may help