Originally Posted by ortho281
Just curious. Why stop using Shell and use Chevron instead? I mostly use Shell, because where I live, they out number Chevron 8:1
Not sure how it is in other states, but I've personally had the worst luck with Shell gas.
Shell threw my car into limp mode a few times, and that same week, a friend of mine with a 335 that filled up with shell at a different station, also went into limp mode. Both cars never saw limp mode before this fill up. After changing gas, no further problems.
It's not a conclusive determination, but I will never use their gas again. I fill up with Chevron pretty much religiously, and if not available I use 76. I definitely miss the Sunoco 94 when I lived on the east coast!
Looking at his AFR, it looks like the car is hitting the targeted AFR's for the most part. Because of how unsmooth the graph is, it looks like this is related to ignition - which could be something wrong with a plug/coil, or a gas issue, etc..
Curious if the car has any shadow codes in there..