Finally it is my turn to ask for help. My wife's 2003 Durango, 2wd, 4.7 Engine runs rough at that particular rpm range. It gets 15.3mpg in town and 18.6 on highway. I replaced the spark plugs with the Champion Copper ones and there is no oil in the plug areas. It has 135,000mi. on it and the only thing that was replaced since we have had it new is, Tps, Waterpump, Clutch Fan, belts, hoses, and new Radiator. Engine always had Mobil 1 Synthetic in it and changed regularly and trans has been serviced every 24,000mi. The engine never ticks at start up and always idled smooth with no noise. Never overheated. Only reason waterpump, radiator and fan was replaced was because the waterpump bearing let loose and sent the fan through the radiator. No codes stored or active. Any suggestions on where I might begin?

 

Run some Seafoam in the tank as it sounds more like a dirty injector than anything.

 

Thanks, I will try that out. I did take off and cleaned the throttle body and ran seafoam through the brake booster vacuum line till the engine stalled. Smoked out the neighborhood after letting it sit for a while and restarting.

 

well that mpg range is not terrible considering they are rated at 13/16 w/ the 4.7 (and the ratings are usually higher than you actually get) of course i tend to get more like 15/19, over my last tank of gas (260-275 miles) i got 17.3 mpgs hand calc'd, keep in mind the firs 80 miles or so was city and rest was pretty smooth cruising on the highway so your gas mileage numbers are not that bad

 

I guess the 5 speed auto works pretty good. With the 3.55 gears on the back I tell her to drive around town with OD off unless she is driving over 45mph. I noticed that it helps the mpg around town a lot better that way. If she has OD on in town, the mpg really drops. I think the 4.7 engines like to run around 1800-2000rpm's for the good mpg's.