M11 Industrial Operation and Maintenance – Engine Runs Rough at Idle

Symptom Tree  

Engine is operating at low ambient temperature

Check the winterfront, shutters, and under-the-hood air. Use under-the-hood intake air in cold weather. Refer to Procedure 101-015 (Operating the Engine) in Section 1.


Electronic fault codes are active

For instructions on how to read active fault codes, refer to Procedure 101-007 (Electronic Controlled Fuel System) in Section 1. If fault codes are active, contact a Cummins Authorized Repair Facility.


Engine mounts are worn, damaged, or not correct

Check the engine mounts. Refer to the OEM service manual.


Engine idle speed is set too low (electronically controlled fuel systems)

Verify the correct idle speed setting. Increase the idle speed with the idle increment switch or an electronic service tool. Refer to Procedure 101-007 (Electronic Controlled Fuel System) in Section 1.


Air in the fuel system

Check for air in the fuel system. Tighten or replace the fuel connections, fuel lines, fuel tank standpipe, and fuel filters as necessary.


Fuel grade is not correct for the application or the fuel quality is poor

Operate the engine from a tank of high-quality fuel. Refer to Procedure 018-002 (Fuel Recommendations and Specifications) in Section V.


Overhead adjustments are not correct

Measure and adjust the overhead settings. Refer to Procedure 003-004 (Overhead Set) in Section 5.

Contact a Cummins Authorized Repair Facility

Last Modified:  19-Nov-2004