hi,need help in this symptom of my car.mine car is auto which had just gone for major servicing recently.had changed timing belt and various belts and also fuel filter.however i had notice when i stopped my car and keep it idleling.my rpm will keep on hunting.the most the rpm hit to 1.4 and after tat went back to normal.When i drive especially when i drive at 90km/h wif rpm 2,my car also will jerk slightly.The feeling is like for those who drive manual gear when ur car did not have certain power to drive the gear,the car will jerk.Can anyone explain to mi wat is the defect?is it due to the belt i have changed ?