Cause | Correction | ||||||||
|---|---|---|---|---|---|---|---|---|---|
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 and lead to a misfire DTC. A misfire code may be present without an actual misfire condition. | Replace the drive belt. Refer to Water Pump and Generator Belt Replacement and/or Air Conditioning Compressor and Power Steering Pump Belt Replacement . | ||||||||
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. | Inspect the components: Repair or replace as required. | ||||||||
Loose or improperly installed engine flywheel or crankshaft balancer A misfire code may be present without an actual misfire condition. | Repair or replace the flywheel and/or balancer as required. Refer to Engine Flywheel Replacement or Crankshaft Balancer Replacement . | ||||||||
Restricted exhaust system A severe restriction in the exhaust flow can cause significant loss of engine performance and may set a DTC. Possible causes of restrictions include collapsed or dented pipes or plugged mufflers and/or catalytic converters. | Repair or replace as required. | ||||||||
Improperly installed or damaged vacuum hoses | Repair or replace as required. | ||||||||
Improper sealing between the intake manifold and cylinder heads, intake manifold and plenum duct, plenum duct and water crossover, water crossover and throttle body and/or pressure relief valve and intake manifold. | Replace the intake manifold, plenum duct, gaskets, cylinder heads, throttle body and/or pressure relief valve as required. | ||||||||
Improperly installed or damaged MAP sensor and/or seal The sealing grommet of the MAP sensor should not be torn or damaged. | Repair or replace the MAP sensor as required. | ||||||||
Improperly installed or damaged EVAP purge solenoid and/or O-ring seal | Repair or replace the EVAP purge solenoid as required. | ||||||||
Worn or loose followers, valve rocker arms The follower, valve rocker arm, roller bearing should be intact and in the proper position | Replace the followers, valve rocker arms, as required. | ||||||||
Stuck valves Carbon buildup on the valve stem can cause the valve not to close properly. | Repair or replace as required. | ||||||||
Excessively worn or mis-aligned timing chain or chains | Replace the timing chain or chains and sprockets as required. | ||||||||
Worn camshaft lobes | Replace the camshaft or camshafts and SHLAs, valve lifters. | ||||||||
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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Faulty cylinder head gaskets and/or cracking or other damage to the cylinder heads and engine block cooling system passages. Refer to Diagnostic Starting Point - Vehicle . Coolant consumption may or may not cause the engine to overheat. |
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Worn piston rings Oil consumption may or may not cause the engine to misfire. |
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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.
| Replace the crankshaft as required. |
