2005 Caravan with a 3.8 intermittant engine ping/rattle

[guinnessbrewer]

Hey all,I have a 05 caravan with the 3.8L which I bought new and now has 70,000 on the clock.Over the years it has had an intermittent ping/rattle under light to heavy acceleration. I typically use 91 octane fuel in it and seems to help a little, but it still happens from time to time. It has happened on cold days and hot days on flat terrain or hilly terrain. Does this engine have a knock sensor? and if it is working shouldn't it back off the timing, if this is a problem?I seem to remember in the 90's dodge had different ecms based on where the vehicle was operating, ( at least on the dakotas and ram gassers)The vehicle was purchased in Georgia with the elevation around 900ft. The vehicle is now typically driven around 4000 to 5000 ft elevation. Could this play into the fuel/air mixture, or should the computer compensate for this? Any clues are appreciated!GB