New Holland 951 – ECM: Power Imbalance Between Cylinders Detected

The Engine Control Module (ECM) hardware has detected a power imbalance between the cylinders, indicating that one or more cylinders are not operating in sync or are not producing equal power output. The ECM continuously monitors engine rotational speed and calculates individual cylinder power contribution by measuring minute crankshaft accelerations as each cylinder fires. If a cylinder's contribution deviates above or below a predetermined threshold compared to the others, this fault is logged. This condition can cause rough idle, engine misfire, power loss, increased fuel consumption, black smoke, may illuminate the amber check engine lamp, and may force the engine into a derated 'limp mode' to prevent damage.

• T4
• T5
• T6
• T7
• T8
• T9
• TM
• TV
• T6010
• T6020
• TS100A
• CR8.80
• CR8.90
• CR9.80
• CR9.90
• L180
• L185
• L190
• C185
• C190
• B95
• B110
• B115
• L225
• L230
• B95C
• TM165
• 8560
• LS180
• T4050
• T5070
• TS6.120
• LS190

1. 1

   Perform a cylinder cut-out test using a diagnostic service tool. This test deactivates one injector at a time to identify which cylinder is underperforming (a cylinder that produces little to no change in engine speed when cut out is the likely source).

2. 2

   Inspect fuel filters for contamination or restriction. Clogged filters are a common cause of power loss and can lead to imbalanced fueling.

3. 3

   Perform a 'bubble test' on the fuel system to check for air intrusion, which can indicate a leak on the suction side of the fuel system.

4. 4

   Check valve lash clearance while the engine is cold (incorrect clearance is a primary cause of this fault; if too tight, valves may not close properly; if too loose, it can cause noise and damage to the valvetrain).

5. 5

   Check for excessive crankcase pressure (blowby), which can indicate damaged pistons, rings, or cylinder walls.

6. 6

   Listen for abnormal noises, such as a 'chirping' sound from the intake, which could suggest a damaged or sticking intake valve.

1. 1

   Address fuel system faults

   If a cylinder cut-out test points to a specific injector, or if fuel system contamination is found, the injector may be faulty. Inspect the injector wiring harness for damage or corrosion. If the wiring is intact, replace the suspect fuel injector. It is often recommended to replace injectors in a full set to ensure balanced performance.

2. 2

   Perform a valve lash adjustment (Overhead Adjustment)

   Ensure the engine is cold and disconnect the battery negative terminal. Remove the rocker arm cover to access the valvetrain. Rotate the engine to bring the piston of the cylinder being adjusted to Top Dead Center (TDC) on its compression stroke. At this point, both rocker arms for that cylinder should be loose. Loosen the locknut on the rocker arm adjusting screw. Use a feeler gauge set to the manufacturer's specifications (e.g., 0.013 inches) and turn the adjusting screw until the feeler gauge has a slight drag between the valve stem and the rocker arm. Hold the adjusting screw in place and tighten the locknut to the specified torque. Re-check the clearance to ensure it did not change during tightening. Repeat the process for all cylinders according to the engine's firing order and adjustment sequence outlined in the service manual.

3. 3

   Address major mechanical faults

   If the above steps do not resolve the issue, a more significant mechanical problem is likely. If a damaged valve or head gasket is suspected, the cylinder head will need to be removed. Inspect the cylinder head for cracks, warping, and signs of gasket leakage between cylinders. Inspect valves, valve seats, and pistons for damage. Replace the cylinder head gasket and any damaged components (valves, valve guides, pistons, rings). Ensure all surfaces are clean and check the cylinder head for flatness before reassembly.