GM Service Manual Online
For 1990-2009 cars only

Condition

Action

Abnormalities (severe cracking, bumps or missing areas) in the accessory drive belt.

Abnormalities in the accessory drive belt 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.

  1. Inspect the accessory drive components.
  2. Repair or replace all damaged components.

Worn, damaged, or misaligned accessory drive components or excessive pulley runout

A misfire code may be present without an actual misfire condition.

  1. Inspect the accessory drive components.
  2. Repair or replace all damaged components.

Loose and/or damaged crankshaft balancer

A misfire code may be present without an actual misfire condition.

  1. Inspect crankshaft balancer and balancer bolt.
  2. Repair or replace all damaged components.

Loose torque converter bolts

A misfire code may be present without an actual misfire condition.

  1. Inspect torque converter bolts and flywheel.
  2. Repair or replace all damaged components.

Loose and/or damaged flywheel

A misfire code may be present without an actual misfire condition.

  1. Inspect flywheel and flywheel attaching bolts.
  2. Repair or replace all damaged components.

Excessive piston-to-cylinder bore clearance

  1. Perform cylinder leak down and compression tests
  2. Inspect the piston, piston rings and cylinder bore.
  3. Repair or replace all damaged components.

Excessive crankshaft thrust bearing clearance

Severely worn thrust surfaces on the crankshaft and/or thrust bearing may permit for and aft movement of the crankshaft and create a misfire code without an actual misfire condition.

  1. Inspect the crankshaft end play and crankshaft thrust bearings.
  2. Repair or replace all damaged components.

Overfilled crankcase

  1. Check engine oil level with vehicle on a level surface.
  2. Correct any overfilled condition.
  3. Inspect for fuel leaks into the crankcase.
  4. Repair any fuel leaks.