Stopped at the gas station a couple days ago to fill up and as I was leaving I noticed a real slight miss while idling through the parking lot. Didn't think much of it at first till last night on my way out of town heading up a hill the miss returned at around 50mph. Noticed it again this morning backing the boat into the landing. Seems to becoming more frequent, however only when the vehicle is warmed up. From what I've read online so far I'm leaning toward o2 sensors. I believe the upstream are the ones that control the air to fuel mix possibly causing a lean condition on one cylinder. Before I drop $100 on a pair I'll probably do a oil change and tuneup since its about that time. I plan on replacing all filters, and checking the cap and rotor as I've had numerous problems with brand new parts from Napa. Any other suggestions as to what to check would be greatly appreciated. For reference there's just shy of 113,000 miles on the truck, intake gaskets were done at aprox 85k, along with distributor replacement since local shop decided to break the stock distributor but not own up to it.

 

I'd try some fuel injection cleaner first, then if no help...go to Advance Auto Parts or Autozone and have them scan your computer...that will tell you whats going on. Good luck!!