My 2018 GMC Denali 1500 started idling rough 10 months ago or so and I read here on the forums that the seafoam spray top engine cleaner & lube could help or fix my issue, which it did. I wouldn't say it fixed the rough idle 100% but it was definitely better! Fast forward to earlier this week we returned home from a 80 day vacation and I noticed the truck idling rougher than ever but intermittently, yesterday wile sitting in line @ Sam's to buy gas it got REALLY bad almost to the point I thought it was going to die! After filling up it seemed better but then it threw a check engine light so I swung into Auto Zone and they read the code which was P0305. Any help is appreciated, think the two are related? Where do I start?
I bought the truck new, it has 54k miles on it, I have always run 87 octane in it.