01 taurus problems need help plz!

I think I'm having a problem with the overdrive transmission. When pulling a hill the car shutters like it wants to downshift but if I let off the throttle it'll go away. Or, step down the throttle and make it downshift it goes away. Also, when coming to a stop, the car shutters like it has a miss. This problem is not all the time. But mostly it happens after coming off a long drive and stopping on or off a ramp. The car misses or shutters sitting still. The same symtoms that it has when pulling a hill.If I run the transmission not in overdrive the problem seems to go away except it'll still get the miss or shutter when I bring the car to a stop or sit idle. It also at one point had the miss or shutter while parking in reverse. The car was scaned and check at our Ford dealership, and no codes were present.Is it a transmission problem or something else? Possible intake leak or vaccum problem. Plz help me out because the warrenty is running out in march and if the car isnt throwing a code the dealer wont do anything about it, i know by the problems im having something is seriously wrong with my car, BTW my car only has 25k miles on it and it has the dohc engine, and having some guys that could give me ideas where to look would help me out alot, thanks for the help

your problem may be arcing through the plug boot to a spark plug, tried to find a similar problem with mine for 4 weeks, remove and clean all plug boots and be sure to use dielectric grease on the boots before reinstalling mine only had 1 cyl doing this, has run perfect since