Wayfarerwalk
Member
I have a 98 EB 5.4 with less than a month old tune, injector and TB clean. It was doing this chugging/missing when I have it tuned. They (local dealer) claimed there were no codes and when I picked it up it did run good for about a week. At the same time, under normal acceleration I was getting pinging from the valves. Ran some premium gas through it for 3 tanks and the missing and pinging stopped along with a mild increase in mileage, plus the acceleration was fantastic. But when I would get to the 1/4 tank mark, the missing would start again. I just put regular back in it and its a missing dog again. Being mechanically challenged I was wondering your thoughts. I was thinking fuel filter (about 6 months old) or fuel pump, but with it running so good on the good stuff, it kinda stumps me. Thanks for any help.