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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 systems and/or components may cause variations in engine speed and lead to a diagnostic trouble code for misfiring. A diagnostic trouble code for misfiring may be generated without misfiring actually 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
May lead to a diagnostic trouble code for misfiring.
A diagnostic trouble code for misfiring can be saved without a misfire occurring.
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Check the components and repair or replace if necessary:
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A 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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Reduced exhaust system
A severe clogging of the exhaust flow may cause a significant deterioration in engine performance and may generate a diagnostic trouble code. Possible causes of clogging may be squeezed or dented pipes or clogged silencer and/or catalytic converters.
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Repair or replace if necessary.
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Incorrectly fitted or damaged vacuum hoses
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Repair or replace if necessary.
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Incorrectly fitted or leaking pipes to charge air cooler
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Repair or replace if necessary.
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Incorrect seal between the intake manifold and cylinder head or throttle body
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Replace the intake manifold, gaskets, cylinder heads and/or throttle body if necessary.
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Incorrectly fitted or damaged sensor for manifold absolute pressure (MAP) or sensor for intake air temperature (TMAP).
The MAP sensor's entry point must not be worn or damaged.
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Repair the MAP sensor and/or TMAP sensor if necessary.
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Damage to the MAP sensor's housing
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Replace the intake manifold.
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Worn or loose rocker arms
The end covers to the valve bridge bearings and/or needle bearings must be intact and in the correct position.
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Replace the rocker arms if necessary.
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Valves that have jammed
Carbon deposits on the valve stem may mean that the valve does not close properly.
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Repair or replace if necessary.
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Heavily worn or misaligned timing chain
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Replace timing chain and sprocket if necessary.
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Worn camshaft cams
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Replace the camshaft and tappets.
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Oil pressure too high
A lubrication system with oil pressure that is too high may lead to the tappets being pumped up, resulting in unsealed valves and then compression loss.
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2.
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Repair or replace the oil pump if necessary.
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Defective cylinder head gaskets and/or cracking, or other damage to the cylinder head and the engine block's cooling ducts.
Use of cooling agents may possibly lead to the engine overheating.
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1.
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Check that there are no spark plugs soaked with cooling agent.
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2.
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Check the cylinder heads, engine block, and/or cylinder head gaskets.
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3.
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Repair or replace 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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A damaged sensor wheel on the crankshaft
A damaged sensor wheel on the crankshaft may cause various symptoms depending on the severity and location of the damage.
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In systems with electronic communication, direct ignition or one coil per cylinder, serious damage to the crankshaft's sensor wheel may cause a periodic loss of crankshaft position, signal stop and then resynchronisation of crankshaft position.
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In systems with electronic communication, direct ignition or one coil per cylinder, minor damage to the crankshaft's sensor wheel does not necessarily cause any loss of crankshaft position and no misfiring occurs. However, the diagnostic trouble code P0300 may be generated.
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In systems with mechanical communication and high-voltage ignition, serious damage to the crankshaft sensor wheel may cause extra pulses and affect fuel supply and ignition until diagnostic trouble code P0300 or P0336 is generated.
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Replace the sensor and/or crankshaft if necessary.
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