N14 Base Engine Troubleshooting and Repair Manual – Engine Speed Surges at Low or High Idle

Electronic fault codes active or high counts of inactive fault codes

Refer to Section TF in the Troublshooting and Repair Manual CELECT™ Plus Systems, Bulletin 3666130, or Section TF in the Troubleshooting and Repair Manual for the CELECT™ Systems, Bulletin 3666084.

Air in the fuel system

Check for air in the fuel system. Refer to Procedure 006-003.

Fuel level is low in the tank

Fill the supply tank. Refer to the OEM vehicle specifications.

Fuel inlet restriction

Check for fuel inlet restriction. Refer to Procedure 006-020.

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

Verify the correct idle speed setting. Increase the idle speed with INSITE™.

Engine idle speed is set too low (mechanical fuel systems)

Adjust the fuel pump idle speed. Refer to Procedure 005-029.

Electronic control module (ECM) calibration is malfunctioning

Verify the ECM calibration is correct. Check the calibration revision history for applicable fixes to the calibration stored in the ECM. Refer to the calibration history spreadsheet Click here to see ecm_calibration_rev_history.xls

on QuickServe® Online or the INCAL™ CD-ROM. Compare the calibration stored in the ECM with the engine rating and the Control Parts List (CPL), Bulletin 4021326 or 4021327. If necessary, recalibrate the ECM. Refer to Procedure 019-032 in the Troubleshooting and Repair Manual for CELECT™ Plus Systems, Bulletin 3666130, or the Troubleshooting and Repair Manual for CELECT™ Systems, Bulletin 3666084.

Fuel drain line restriction

Check or replace the fuel lines, check valves, or tank vents as needed. Refer to Procedure 006-012.

Injector is malfunctioning (CELECT™ and CELECT™ Plus)

Perform the automated cylinder performance test. Replace injectors as necessary. Refer to Procedures 006-005 and 006-026.

Engine position sensor (EPS) or circuit is malfunctioning

Check the engine position sensor and circuit. Refer to Procedures 019-038 and 019-039 in the Troubleshooting and Repair Manual CELECT™ Plus Systems, Bulletin 3666130, or the Troubleshooting and Repair Manual CELECT™ Systems, Bulletin 3666084.

Vehicle speed sensor (VSS) or circuit is malfunctioning

Use an electronic service tool to monitor the vehicle speed while the vehicle is not moving. Refer to the appropriate electronic service tool manual. If the monitor shows speed, check the sensor and circuit. Refer to Procedures 019-090 and 019-091 in the Troubleshooting and Repair Manual CELECT™ Plus Systems, Bulletin 3666130, or the Troubleshooting and Repair Manual CELECT™ Systems, Bulletin 3666084.

Injector is malfunctioning (PT/STC)

Remove and check the injectors. Replace injectors as necessary. Refer to Procedure 006-026.

Automotive and variable speed (VS) governor idle speeds are set too close (STC engines only)

Adjust the automotive and VS idle speeds. Refer to Procedures 005-028 and 005-029.

Auxiliary governor (if equipped) is not adjusted correctly

Adjust the idle speed above the engine fuel pump idle speed setting. Refer to the manufacturer’s instructions.

Throttle linkage adjustment is not correct

Check the fuel pump throttle linkage adjustment. Refer to Procedure 005-036.

PT fuel pump calibration is not correct

Remove the fuel pump. Check the calibration. Refer to Procedure 005-016 and PT Fuel Pump Rebuild and Calibration Manual, Bulletin 3379084.

PT fuel pump is not assembled correctly

Check the fuel pump for correct assembly and installation. Refer to Procedure 005-016 and PT Fuel Pump Rebuild and Calibration Manual, Bulletin 3379084.

Camshaft end clearance is excessive

Check the camshaft end clearance. Refer to Procedure 001-065.