1998 dodge neon tranny problem?

[morticar2]

1998 dodge neon sohc automatic. Driving constant speed over 45 the engine surges from what appears to be the tranny coming in and out of overdrive. There is no rhyme or reason it doesnt when it wants to, no codes, trany fluid clean and full, it will only last a second or two then either stay in od or out of it for a while then jump back and forth. IT will do it for an hour trip and then on the way back it wont do it at all or a couple of time and then quit. Everything looks hooked up, readjusted the throttle pressure cable no change. Im stumped. The only codes i have showing is emmisions i have a bad purge valve not hooked up been that way since i had the car two years ago with none of this problem ever happening. Any help would be appreiciated. thanks