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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.
Malfunctions in the auxiliary drive system and the components can cause fluctuations in the engine speed which may be registered as a fault code for misfiring. A fault code for misfiring may be set without there actually having been any misfiring.
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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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Loose or improperly installed 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 and repair or replace as required.
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Loose or improperly installed engine flywheel
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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Air in fuel system
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Inspect fuel filter, fuel system for leaks and/or restrictions and repair or replace as required.
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Bent and/or worn valve pushrod
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Inspect valve pushrod and valve rocker arm and repair or replace as required.
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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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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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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 belt
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Replace the timing belt and sprockets as required.
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Damaged or misaligned timing gears
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Inspect timing gears and replace as required.
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Worn or faulty camshaft lobes
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Replace the camshaft and valve lash adjusters.
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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 gasket and/or cracking, or other damage to the cylinder head and engine block cooling system passages.
Coolant consumption may or may not cause the engine to overheat.
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Inspect the cylinder head, engine block, and/or head gasket.
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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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Perform cylinder leak down and compression testing to identify the cause.
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Repair or replace as required.
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Overfilled Crankcase
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Check engine oil level with vehicle on a level surface.
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Correct any overfilled condition.
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