I have a 99 Durango SLT 5.9 with only 91k miles on it. when it cools down it doesnt want to idle got from 1000 rpm to 500 rpms or it cuts off..when u are driving down the road the tranmission is acting funny as well it all started at the same time some times it runs strong. woke up one morning and it started all of this.... PLZ HELP!!!!!!!