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Home >> Saturn >> 2006 >> Relay 3.9 1, FWD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 1 (Engine Mechanical - 3.5L) >> Diagnostic Information and Procedures >> Base Engine Misfire with Abnormal Internal Lower Engine Noises

Base Engine Misfire with Abnormal Internal Lower Engine Noises

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Base Engine Misfire with Abnormal Internal Lower Engine Noises

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 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.
  1. Inspect the spark plugs for oil deposits. Refer to Spark Plug Inspection .
  2. Inspect the cylinders for a loss of compression. Refer to Engine Compression Test .
  3. Perform cylinder leak down and compression testing to determine the cause.
  4. 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.