Ive been trying to get this issue with my car idling @ about 550-600 rpm when @ normal operating temp. And when it finally gets to normal operating temp when I sit in "drive" the rpms tend to flutter and the car seems to want to stall. But it only does this after the car has gotten up to operating temp. Could this be a result of a worn timing chain? the car has 165K miles on it and I have owned it for 4 years and it hasnt been changed since ive had it. I bought it with 135K miles on it.