| Cause | Correction |
|---|---|
| Abnormalities consist of severe cracking, bumps or missing areas in the accessory drive belt Abnormalities in the accessory drive system and/or components may cause engine RPM variations, noises similar to a faulty lower engine and also lead to a misfire condition. A misfire code may be present without an actual misfire condition. | Replace the drive belt. Refer to Drive Belt Tensioner Replacement . |
| Worn, damaged, or mis-aligned accessory drive components or excessive pulley runout A misfire code may be present without an actual misfire condition. | Inspect the components, repair or replace as required. |
| Loose or improperly installed engine flywheel or crankshaft balancer A misfire code may be present without an actual misfire condition. | Repair or replace the flywheel and/or balancer as required. Refer to Engine Flywheel Replacement or Crankshaft Balancer Replacement . |
| Worn Piston Rings Oil consumption may or may not cause the engine to misfire. | Inspect the spark plugs for oil deposits. Refer to Spark Plug Inspection in Engine Controls. Inspect the cylinders for a loss of compression. Refer to Engine Compression Test . Perform cylinder leak down and compression testing to determine the cause. Repair or replace as required. |
| Worn Crankshaft Thrust Bearings Severely worn thrust surfaces on the crankshaft and/or thrust bearing may permit fore and aft movement of the crankshaft and create a DTC without an actual misfire condition. | Replace the crankshaft and bearings as required. |
Base Engine Misfire with Abnormal Internal Lower Engine Noises