Have a 2004 1500 4.7L SLT throwing a p0308 code. I have changed the spark plugs with new copper plugs, new coil packs, flashed the pcm removed valve cover and checked for a dropped lifter(was none) and after driving 150-200 miles the 308 code is coming back. I purchased decent coil packs and not the cheap amazon ones. Wondering what my next steps should be. I’m getting no other codes and the truck is driving fine. Only other thing I am noticing is, at idle in park it will rev on its own to 1200rpm then drop back to normal idle. It will only do this once. Would a fuel injector cause this code?

just picked up the truck last week for a pretty good deal. Previous owner had it for 14 years and purchased it off his father in law who purchased it new from the dealer. In great condition and well cared for. He got a diagnosis from a Honda dealer for a head gasket after they did some generic tests but I’m not seeing any signs of a head gasket issue, i.e. no smoke, no loss of coolant, no water in the oil. Think I got a good deal for $3,300. Would just love to clear the code for good.

 

Try swapping the injector with the one next to it. See if the miss moves with the injector.