Basic engine misfiring with abnormal internal noise in lower part of the engine (A20NFT/LHU)
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Basic engine misfiring with abnormal internal noise in lower part of the engine (A20NFT/LHU)
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Cause
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Procedure
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Deviations, sharp cracks, bumps or missing areas on accessory drive belt
Deviations in the accessory drive system and/or components may cause variations in engine speed, noise similar to a defective lower engine and also misfiring. A diagnostic trouble code for misfiring can be saved without a misfire occurring.
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Replace the drive belt.
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Worn, damaged or misaligned components in the accessory drive or excessive lateral runout for pulley
A diagnostic trouble code for misfiring can be saved without a misfire occurring.
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2.
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Repair or replace components if necessary.
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Loose or incorrectly fitted flywheel or balance weight for the crankshaft
A diagnostic trouble code for misfiring can be saved without a misfire occurring.
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Repair or replace the flywheel and/or balance weight if necessary.
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Worn piston rings
Oil consumption may cause the engine to misfire.
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1.
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Check for oil deposits on the spark plugs.
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3.
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Carry out a leakage test and compression test on the cylinders to determine the cause.
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4.
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Repair or replace if necessary.
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Worn thrust bearings crankshaft
Heavily worn pressure surfaces on the crankshaft and/or thrust bearing may cause the crankshaft to move too early or too late, and generate a diagnostic trouble code without a misfire occurring.
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Replace the crankshaft and bearings if necessary.
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