Engine running/idling rough

Without knowing any other details or even which engine you have, I'd start with the basics, spark plugs and wires. Some engines use a coil pack and one bad ignition coil in it will kill two cylinders. Check for diagnostic fault codes too. Chrysler makes that real easy. Cycle the ignition switch three times from "off" to "run" within five seconds, leave it in "run", then watch the numbers show up in the odometer display.