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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 revolutions per minute (RPM) variations and lead to a misfire diagnostic trouble code (DTC). 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 may lead to a misfire DTC.
A misfire code may be present without an actual misfire condition.
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Inspect the components, and repair or replace as required.
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A 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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Restricted exhaust system
A serious blockage of the exhaust flow can cause significantly impaired engine performance which may be registered as a fault code. Possible causes of blockage are squashed or buckled pipes or clogged silencer and/or catalytic converter.
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Repair or replace as required.
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Improperly installed or damaged vacuum hoses
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Repair or replace as required.
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Improper sealing between the intake manifold and cylinder heads or throttle body
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Replace the intake manifold, gaskets, cylinder heads, and/or throttle body as required.
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Improperly installed or damaged manifold absolute pressure (MAP) sensor
The sealing grommet of the MAP sensor should not be torn or damaged.
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Repair or replace the MAP sensor as required.
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Damage to the MAP sensor housing
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Replace the intake manifold.
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Worn or loose rocker arms
The rocker arm bearing end caps and/or needle bearings should be intact and in the proper position.
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Replace the valve rocker arms as required.
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Stuck valves
Carbon buildup on the valve stem can cause the valve not to close properly.
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Repair or replace as required.
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Excessively worn or mis-aligned timing chain
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Replace the timing chain and sprockets, as required.
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Worn camshaft lobes
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Replace the camshaft and valve lifters.
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Excessive oil pressure
A lubrication system with excessive oil pressure may lead to excessive valve lifter pump up and loss of compression.
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Repair or replace the oil pump as required.
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Faulty cylinder head gaskets and/or cracking or other damage to the cylinder heads and engine block cooling system passages
Coolant consumption may or may not cause the engine to overheat.
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Inspect for spark plugs saturated by coolant.
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Inspect the cylinder heads, engine block, and/or head gaskets.
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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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Inspect the spark plugs for oil deposits.
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Perform cylinder leak down and compression testing to identify the cause.
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Repair or replace as required.
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A damaged crankshaft reluctor wheel
A damaged crankshaft reluctor wheel can result in different symptoms depending on the severity and location of the damage.
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Systems with electronic communications, DIS or coil per cylinder, and severe reluctor ring damage may exhibit periodic loss of crankshaft position, stop delivering a signal, and then re-sync the crankshaft position.
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Systems with electronic communication, DIS or coil per cylinder, and slight reluctor ring damage may exhibit no loss of crankshaft position and no misfire may occur. However, a DTC P0300 may be set.
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Systems with mechanical communications, high voltage switch, and severe reluctor ring damage may cause additional pulses and effect fuel and spark delivery to the point of generating a DTC P0300 or P0336.
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Replace the sensor and/or crankshaft as required.
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