Weird sputtering issue

Hi all,

Well I took it out again today and it was fine for the first 15-20 minutes.
Then it started sputtering so I pulled over and felt the coil and it was not hot.
I also removed the gas cap and there was a good amount of pressure that escaped. I left the gas cap off but it didn't seem to help.

Same as before, I waited about 5-10 minutes and the car started and
ran fine till I got it home.
:scratch::-k

Thanks for the info on the coil grounding. Positive side sounds right.