95-97 Ford 7.3 L DIT Powerstroke – Cylinder Contribution Test


Reference Number(s): 97-26-18, Date of Issue:  December 22, 1997


Rough Idle – 7.3L DIT – New Cylinder Contribution Test – Service Diagnostic Tip




Model(s): Ford Light Truck: 1995-97 F Super Duty, F-250, F-350

1996 Econoline

Bulletin No.: 97-26-18

Date: December 22, 1997

Calibration: 6-89A-R10, 6-90A-R10, 6-90B-R10, 6-90D-R12, 7-89A-R10, 7-90A-R10, 7-90J-R10

WARNING: This modification is authorized only for the listed engine. Performing this modification on other engine calibrations is unauthorized and could create liability under applicable federal or local laws.



A rough idle may occur on some vehicles. This may be caused by a faulty injector.



If the Powertrain Control/Emissions Diagnosis (PC/ED) Service Manual does not pinpoint the cause of the rough idle, reprogram the Powertrain Control Module (PCM) to allow for a more accurate Cylinder Contribution Test (CCT) which will help identify an injector that may not be operating as intended. Refer to the following SERVICE PROCEDURE  for details.


  1. Diagnose concern by referring to the appropriate model year PC/ED, Performance side. Continue to the next step if the following items (any of which require service) do not correct the rough idle condition:
    • Dirty fuel
    • Low fuel pressure
    • Low oil level
    • Air in fuel system
    • Oil aeration
    • System electrical fault
    • Injection Pressure Regulator (IPR) valve or Injection Control Pressure (ICP) sensor
    • Base engine, mechanical fault
    • Faulty injector assembly
      NOTE: When looking at oil aeration, run engine at 3400 rpm for 3 minutes. If ICP goes above 1400 psi (non-rate shaped injectors only) and after returning to an idle, the engine runs rough for a minute or so, but smoothes out, replace the oil.
  2. Reprogram the PCM using the latest level CD-ROM. Refer to the following RECALIBRATION CROSS REFERENCE TABLE  for correct PCM usage.
  3. Engine Operating Temperature (EOT) needs to be at minimum 77°C (170°F) to run CCT. Using the New Generation Star (NGS) Tester, monitor the EOT Parameter Identification Display (PID), determine at what EOT the idle quality is worst. Run the CCT at that temperature. If no codes were generated by the first test, repeat CCT at different temperatures until a code is displayed identifying the cylinder(s) at fault.
  4. Inspect for engine component damage (e.g., push rods, rocker arms). If no engine component problems were found, replace the injector(s) identified with a fault code by referring to the appropriate model/year Service Manual for details.
  5. After replacing an injector or opening the high pressure oil system, the engine will run rough until all of the air is self-bled out of the system through the injectors. This is best accomplished when the engine is worked hard. Do not rerun CCT until all the air is removed from the system.
    NOTE: If an injector is the cause, only 49-state (non-rate shaped) injectors are to be used, for all of the listed calibrations.
  6. Record all codes generated by the CCT on the performance diagnostic sheet and send to Warranty Parts Return Center according to normal warranty claim procedures.

Old Calibration Old Part Number (-12A650-) New Calibration New Part Number (-12A650-)
6-89A-R10 F7TF-SA 6-89A-R11 F7TF-SB
6-90A-R10 F6TF-AYF 6-90A-R11 F6TF-AYG
6-90B-R10 F6TF-AZF 6-90B-R11 F6TF-AZG
6-90D-R12 F6UF YG 6-90D-R14 F6UF-YH
7-89A-R10 F7TF-SA 7-89A-R11 F7TF-SB
7-90A-R10 F7TF-TA 7-90A-R11 F7TF-TB
7-90J-R10 F7TF-UA 7-90J-R11 F7TF-UB

Obtain an Authorized Modification Decal (FPS 8262 – obtainable through DOES II, 25/pkg) and list the date, dealer number, and summary of modifications performed. See Fig 1 . Select a prominent place adjacent to the Vehicle Emission Control Information Decal suitable for installing the Authorized Modifications Decal. Clean the area, install the decal, and cover it with a clear plastic decal shield.


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