Base Engine Misfire with Abnormal Internal Lower Engine Noises
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Base Engine Misfire with Abnormal Internal Lower Engine Noises
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Cause
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Correction
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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.
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Replace the drive belt.
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Worn, damaged, or mis-aligned accessory drive components or excessive pulley runout
A misfire code may be present without an actual misfire condition.
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Inspect the components, repair or replace as required.
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Loose or improperly installed engine flywheel or crankshaft balancer
A misfire code may be present without an actual misfire condition.
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Repair or replace the flywheel and/or balancer as required.
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Loose torque converter bolts
A misfire code may be present without an actual misfire condition.
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Inspect the torque converter bolts and flywheel. Repair or replace as required.
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Worn piston rings
Oil consumption may or may not cause the engine to misfire.
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2.
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Perform cylinder leak down and compression testing to identify the cause.
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3.
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Repair or replace as required.
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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 misfire code without an actual misfire condition.
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Replace the crankshaft and bearings as required.
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Overfilled Crankcase
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1.
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Check engine oil level with vehicle on a level surface.
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2.
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Correct any overfilled condition.
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3.
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Inspect for fuel leaks into the crankcase.
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4.
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Repair any fuel leaks.
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