Q: 2007 Ford focus sputters when idling and check engine light is on

Hi there. In most cases, when the check engine light is illuminated, it’s due to a sensor or vehicle system recognizing a problem and storing an on board diagnostic (OBD-II) in the ECU and triggering the warning light. When your engine idle is rough and shaky, it’s commonly due to a vacuum leak, dirty or clogged fuel injectors or other fuel system problems. It’s also possible that spark plugs or plug wires are worn out, or there is a different ignition system component that is causing an engine misfire. The best way to isolate the source of this problem, is to have a professional mobile mechanic come to your location and complete a car idle is rough inspection. Once they diagnose the root source of the problem, they will be better qualified to resolve this problem.