For 1990-2009 cars

Cause | Correction
--- | ---
Abnormalities, 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 Water Pump and Generator Belt Replacement and/or Air Conditioning Compressor and Power Steering Pump 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. | 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 engine flywheel and/or crankshaft balancer as required. Refer to Engine Flywheel Replacement or Crankshaft Balancer Replacement .
Worn or broken 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.

• | 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.