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Home >> Hummer >> 2008 >> H2 4D Utility Wagon >> Repair and Diagnosis >> External Pages >> Different car >> Section 152 (Engine Mechanical - 4.8L, 5.3L, 6.0L And 6.2L (1 Of 5)) >> 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, 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 - Accessory .
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 and repair or replace, as required.
Loose or improperly installed engine flex plate or crankshaft balancer
A misfire code may be present without an actual misfire condition.		 Repair or replace the flex plate and/or balancer, as required.
Refer to Automatic Transmission Flex Plate 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. Refer to Cylinder Leakage Test .
  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.
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