Engine light shows I have a bad fuel injector. Truck runs rough at idle but at 6

what did the noid light test show?

Hi Steve, You have to be careful on these type of problems may cause more damage in the short term. Fuel Injectors could be defective and causing a washing condition in the engine cylinders and possible damage to the catalytic converter. Best thing to do is bring it in and have it diagnosed. Thank You Ultimate Performance Team 951 360-8518