ok. this has been going on for quite a while now. actually there are two problems. one is when i go down a hill in any gear (auto) the resistance i guess between the crankshaft from the engine and the shaft from the transmission is in perfect harmony so this is my theory, when the shafts from both tranny and engine are moving with no resistance on eachother, i guess the engine wants to try to have resistance by moving the rev up and down while the throttle being totally out (as in foot off the petal) well when it finally does get resistance the rev up and down stops, but if you go down a hill again, it does it again until the engine and tranny are resisting eachothers pull. anyways heres another problem. when i start off in gear (in cold start or hot weather) no matter what gear it is, it seems like my injectors are not working right because when the tachometer reaches about 1700 rpm to about 2000 rpm the engine starts "bubbling" its kind of like when you take off in too high of a gear in a 5 speed except mines an auto. so anyways i put fuel injector cleaner (stp) and it didnt do anything. it gets really aggravating when your engine sounds like a tractor when your taking off. as i said it happens in every gear so i try to keep it above 2000 rpm.