Original owner purchased new in May of 17. Was fine until about this summer when we were camping (i had forgotten it first started 6 months ago) and it did the two full start cycles to get it to start. Didn't think much of it as I had gassed up at a rural gas station and the truck had sat in the high altitude (about 10,500') for a few days. Didn't start happening again until about October.
Now that it's cold (ish) here in Denver, it's doing it almost every time I start it after it's sat for 8+ hours. All kinds of gas brands, Top Tier, different octanes, all of it. Still stumbles. Even ran 2 doses of Techron through it in case it was a dirty fuel system. Didn't help. That's when I started googling.
What's weird though is when I ran it down to empty and added the Techron with 12 gallons of Premium Shell, it ran fine. When I gassed up (after running out the Techron) with about 19 gallons (I have the 38 gallon tank) my usual Phillips 76 85 octane (our regular gas, and what I've always used), the next day it started stumbling again. Filled it to full with Premium (in case the 85 octane was the issue) so now I've got probably 88 octane or so, it still runs like hell.
