Recent issue with my 2010 Scion tC.

Hello, rough running at idle while in gear -- or under load -- is a sign of an engine performance challenge. Ignition spark, fuel delivery, air and fuel mixture ratios can all be at fault. Emissions control components can also negatively influence engine idle and power when they malfunction. As a result, only hands on testing with proper diagnostic equipment and shop manuals for reference is going to get you the results you are seeking. www.repairpal.com/repair-shops