I have a problem withmy chevy. I am running it on petrol but when it gets to about quarter a tank, the car starts jerkin. i got it tuned and everything but the problem seems to remain. kindly if anyone can be of assistance. my email is firstname.lastname@example.org
When it starts jerking, open the fuel filling cap, if it becomes normal. then close it and again drive, if problem finishes, something with cap/vacuum.
2nd option get the fuel pump line checked in the fuel tank, if it is at it's fix place to suck.