Very slight roughness at idle, just noticeable.
Running E85 but it was there on regular 87 octane as well, no ticks or noises, so I'm thinking O2 sensor or something fuel related.
Once off idle - runs perfect, zero complaints.
Any idea what might be the issue?
My 03 is the same way and isnt accompanied by any DTCs or other drivability symptoms. Just like yours, mine runs perfect (I have a slight tick owing to a minor exhaust leak at #7). Its been that way for 10 years / 100k miles.
If you're so inclined, you can always stick a scan tool w/live data, idle it then drive it around while you look at (or a helper looks while you're driving) engine / fuel / emissions data streams to see if anything unusual appears. I do the same every so often and never see anything...maybe fuel filter which if it hasnt been changed in a while, you can do that to see if anything changes (my slight "idle rumble" didnt when i replaced my fuel filter)
Don't worry about it unless it gets worse, DTCs set, fuel mileage drops or you fail emissions testing (if you're unfortunate enough to be subjected to such testing).
Perhaps others will weigh in w/more ideas/suggestions.
