2006 Nissan X-Trail idling of engine

The engine of My X-trail would die down when I'm travlelling. I will however shift immediately to "N" to coast and restart the engine without any problem. This will occur again a couple of times when running specially when I accelerate and then suddenly release the accelerator pedal. What I did was to clean the throttle valve assembly. I simply sprayed a de-greaser solution to the part assembly and did not even attempt to change the position of the butterfly. It was in fact in a closed position when I checked it. It was covered with dirt that it didnt even have a slight opening on the sides. After spraying the part with a de-greaser and wiped it clean with cloth, It showed a slight opening on the sides which I assume to be just normal since all the dirt had been taken out. Incidentally, I did this process without detaching the wiring harness connector from the throttle valve assembly. When I replaced it back and ran the engine, the idling increased to 1,500 rpm to almost 2,000rpm at "N". When I shift to "R" or "D", it would go down to about 1,000 to 1,100rpm. The engine doesn't die down anymore unlike the time before I cleaned the throttle valve. The rpm is now my new concern. May I please know your advise on how to fix this problem?
Thanks. Sonny