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 Drive Belt Tensioner 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, and 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 or throttle body. | Replace the intake manifold, gaskets, cylinder heads, and/or throttle body as required. | ||||||||
Worn or loose rocker arms (The rocker arm bearing end caps and/or needle bearings should be intact and in the proper position. | Replace the valve rocker arms as required. | ||||||||
Worn or bent pushrods | Replace the pushrods. | ||||||||
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 | Replace the timing chain and sprockets as required. | ||||||||
Worn camshaft lobes | Replace the camshaft and 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 A Diagnostic Starting Point - Engine Cooling. 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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