Q: Car sputtering while idling.

There could be a number of issues that can cause this concern. If the issue only occurs after the engine has warmed up. A problem in the electronic throttle control actuator either in the motor or one of the sensors contained in the actuator assembly could be to blame. A faulty mass airflow sensor or oxygen sensor could be incorrectly calculating the air/fuel mixture. Dirty or clogged fuel injectors causing fuel puddling instead of atomization can cause a stumble at idle. Low fuel volume could also be an issue or a faulty engine computer if the issue happens even on a cold startup. The first step would be to read out the fault memory in the engine computer to see if there are any faults stored and then to look at the engine computer operating parameters with a scan tool. You may want to enlist the help of a mechanic, like one from YourMechanic, to use a scan tool to look at faults and engine operating parameters in order to get the diagnosis moving in the right direction and ultimately the final repair.