07 F250, 23K on clock. Drive train stock except straight through muffler & coolant by-pass filter. Notice a slight stutter-stammer in all gears, all speeds, esp when towing my 21" Artic Fox fiver in mtns. Almost like a grounded plug wire in gasser. No ck eng light, or other abnormalities observed. Brought it to Bickford Ford, in Snohomish WA. Dealer tech says no codes, drives fine, unable to determine customer concern. Says EGR tests OK. OEM Oil & fuel filters changed on regular basis. Oil (Delo) @ 200 Hrs, fuel ea other oil chg. Burning b5, combined mileage in 15s stop & go & hwy apx 50% each. Any suggestions? Thanx.

 

Probably an injector sticking if I had to guess. Any smoke at all? I would buy a bottle or two of Rev-X and try it out. If it goes away, then it is a sticky injector. Not much you can do about it unfortunately unless you pay to replace it yourself.

 

thanx, will try it. It can't hurt. Tech report said KOER - Pass. What do initials stand for? Key on engine running ...?