Truck Running Strangely
So ive had this problem since i bought the truck and never thought anything from it and i replaced the ICP thinking that it was what was causeing it. When the truck is warm/ after ive been driving it and have pulled into a parking spot and have it in park, the truck's idle wavers. It will sit at 650 rpms then bogs down and the rpms drop to about 630. The truck shakes pretty good and then it comes back up to above 650 rpms then drops back down again to 630 and it will continue to do this until i have put it in drive or reverse. I notice the drop on my Tach on the dash and on my Auxilary powertrain control module and in my oil pressure guage. It is annoying and like i said it has done this since i got the truck. My question is could it be the cam sensor. Since i have done many oil changes and Fuel filter changes since i got the truck i have ruled those things out...I changed the ICP and there are no codes other than the code thrown by my chip. The truck did this even before i any kind of programmer or chip so ive ruled this out. I don't know what it could be other than the cam sensor or the torque converter is messing with me but i have no tranny problems and my tranny temps rarely get above 160 degrees. So i need so one else to think about this for me because im pulling hair out trying to get the idle to stay constant at 650 which is where its supposed to be.