3. Rough Idle or Slight Miss. Another symptom of 5.9 Cummins bad injectors is a rough idle. If the 5.9 is not idling smoothly or has a slight misfire, then it’s a sign that there’s an issue with the injector’s armature valve, plunger, or the nozzle pintle. A rough idle can be caused by a few different things, but one of the most common Thank you for watching this video !Hubitools HU41010 Diesel Injector Seal Extractor is the most universal and powerful tool to remove a diesel injector seal kV46Nr.