For 1990-2009 cars

Cause | Correction
--- | ---
Abnormalities such as 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 Replacement .
Worn, damaged, or mis-aligned accessory drive components or excessive pulley runout A misfire code may be present without an actual misfire condition. |

1. Inspect the components.
2. Repair or replace the components, 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 .

• | Inspect the cylinders for a loss of compression. Refer to Engine Compression Test .

• | Perform cylinder leak down and compression testing to determine the cause. Refer to Cylinder Leakage Test .

• | Repair or replace components, 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. |

1. Inspect the crankshaft endplay.
2. Replace the crankshaft and/or bearings, as required.