Fuel Injector Balance Test with Tech 2 Manual Transmission

The fuel injector balance test is performed when a misfire, knock, excessive smoke, or rough running condition exists with no electrical DTCs. This test uses the Balance Rate and Cylinder Power Balance test to identify cylinders that are not producing the designed power output. The balance rate adjustments are utilized by the engine control module (ECM) only at idle. The balance rates are the fuel adjustments for each individual cylinder based on the variations in engine crankshaft speed. The balance rates will change depending on if the transmission is in Neutral or Drive. During the Cylinder Power Balance portion of the test, the ECM turns OFF individual injectors while the engine is running. The ECM adjusts for the drop in engine RPM during cancellation and may not change on the scan tool display. The lack of power at the cancelled cylinder will feel like a misfiring cylinder or vibration. If a fuel injector is turned OFF and there is a no difference felt when compared to the other cylinders, that cylinder is identified with the concern. If the customer concern occurs during idle or during off-idle tip in acceleration, the balance rates are used to identify the cylinder with a fault related to the fuel injector or engine compression.

If the majority of the balance rates are positive and high, the dual-mass flywheel is causing a harmonic vibration that is affecting the engine fuel control system.

A dual mass flywheel concern will cause the balance rates to be inaccurate. The transmission concerns must be repaired before any fuel system diagnostic can be performed.

The Cylinder Power Balance Test may be performed at any engine speed or load from idle to wide open throttle (WOT). There is a 5-minute time limit for each test.

A high balance rate may be caused by a fuel injector or compression only if the ECM can control fuel pressure.

Observe the Balancing Rate parameters with a scan tool. Normal reading should be between +4 mm³ and -4 mm³ at idle. With the engine running at idle, the Actual Fuel Rail Pressure should be close to the Desired Fuel Rail Pressure.

If any DTCs other than DTC P0300, P0301-P0308 are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle .

1. Start and run the engine until the ECT is more than 82°C (180°F).
2. Turn OFF all accessories.
3. Perform the fuel pressure regulator test. Refer to Fuel Pressure Regulator Diagnosis .

⇒	If the fuel pressure regulator graph was not normal, replace the fuel pressure regulator. Refer to Fuel Pressure Regulator Replacement .

4. Place the transmission in Neutral and apply the parking brake.
5. Hold the brake pedal in the fully applied position. A hiss will be noticeable when the brake is fully applied.
6. Idle the engine for more than 30 seconds.
7. Record the Balancing Rate Cyl.1-8 parameters from the scan tool while the engine is at idle speed.

⇒	If at least 5 of the Balancing Rates are more than +4 mm³, refer to Engine Flywheel Replacement .

⇒	If the Balance Rates are not between +4 mm³ and -4 mm³ at idle, perform the Cylinder Power Balance Test in Special Functions.

Important: The Cylinder Power Balance Test must be performed under the conditions for which the concern occurred. The concern must be duplicated during the test.

8. Record any cylinders that indicate a different cylinder power contribution and compare the Balance Rates previously recorded with the Cylinder Power Balance results.

⇒	If the Balance Rates were not high or the Cylinder Power Balance test did not indicated a cylinder with a different power contribution, refer to Diagnostic Aids.

Important: A fuel injector leak into the combustion chamber may result in mechanical damage to the cylinder. If any fuel spray comes out of a glow plug hole during the compression test, replace the fuel injector of the affected cylinder.

9. Perform the engine compression test. Refer to Engine Compression Test .

⇒	If the compression test indicated any of the cylinder had low compression, refer to Symptoms - Engine Mechanical .

Important: Refer to Injection System Components in Engine Controls Component Views . Failure to correctly identify the cylinder positions may result in the replacement of the wrong fuel injector.

Important: During replacement of the injectors, inspect the inlet and outlet fittings of the injectors for corrosion or contamination. Refer to Contaminants-in-Fuel Diagnosis .

10. If the engine did not have low compression on any of the cylinders, replace the fuel injectors on the cylinders that had poor cylinder power contribution, high balance rates, or a noise/smoke change during cancellation. Refer to Fuel Injector Replacement .
11. Operate the vehicle under the conditions in which the concern occurred.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Fuel Injector Balance Test with Tech 2 Automatic Transmission

The fuel injector balance test is performed when a misfire, knock, excessive smoke, or rough running condition exists with no electrical DTCs. This test uses the Balance Rate and Cylinder Power Balance test to identify cylinders that are not producing the designed power output. The balance rate adjustments are utilized by the engine control module (ECM) only at idle. The balance rates are the fuel adjustments for each individual cylinder based on the variations in engine crankshaft speed. The balance rates will change depending on if the transmission is in Neutral or Drive. During the Cylinder Power Balance portion of the test, the ECM turns OFF individual injectors while the engine is running. The ECM adjusts for the drop in engine RPM during cancellation and may not change on the scan tool display. The lack of power at the cancelled cylinder will feel like a misfiring cylinder or vibration. If a fuel injector is turned OFF and there is a no difference felt when compared to the other cylinders, that cylinder is identified with the concern. If the customer concern occurs during idle or during off-idle tip in acceleration, the balance rates are used to identify the cylinder with a fault related to the fuel injector or engine compression.

Important: If any DTCs other than DTC P0300-P0308 are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle .

1. Start and run the engine until the coolant temperature is more than 82°C (180°F). Turn OFF all accessories.
2. Perform the fuel pressure regulator test, refer to Fuel Pressure Regulator Diagnosis .
3. Apply the parking brake and hold the brake pedal in the fully applied position. A hissing noise will be noticeable when the brake pedal is fully applied. Place the transmission in Drive and idle the engine for a minimum of 30 seconds. With a scan tool, observe the balancing rates parameters for cylinders 1-8 while the engine is at idle speed. Repeat this procedure with the transmission in the Park or Neutral position. Balance Rates should be between +4 mm³ and -4mm³ in Park or Neutral and +6mm³ and -6mm³ in Drive.

Important: 

•	The Cylinder Power Balance Test must be performed under the conditions for which the customer concern occurred.

•	Do not operate the cruise control during this test. Cruise control may cause a brief surge of engine speed after the completion of the test.

4. Perform the Cylinder Power Balance Test with a scan tool. During cylinder cancellation a noticeable power difference will feel like a misfiring cylinder or vibration.

Important: 

Perform the engine compression test. Refer to Engine Compression Test .

Important: 

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.